In 2007 I was an aspiring young novelist with a manuscript that had been rejected by 43 literary agents. This was at a time when every single submission – which included a personalised letter, three chapters, a synopsis and a self-addressed envelope enclosed for the rejection slip – had to be printed out and sent by post. Nevertheless I remained optimistic, because the 44th agent I contacted wrote back to me, requesting to read my manuscript in full on an exclusive basis. I was certain this was going to be my big break.

A couple of weeks later, I experienced a whole new level of rejection when my manuscript was sent back to me again, with a polite and emphatic thanks-but-no-thanks cover letter.

The unwanted parcel had arrived just as I was on my way out to work and when I got there, I wept. I firmly believed at the age of 28 that my dream of publication was over. A colleague asked me what was wrong. I told her and she was surprisingly sympathetic. “I know a published novelist,” she said. Before I could think to ask, she had offered to facilitate an introduction for me. Perhaps this person could give me some good advice?

That novelist was Hilary Mantel.

At the time Hilary was a well-established author of fiction and memoir. But this was two years before Wolf Hall was published and the stellar success that was to follow. The Wolf Hall trilogy were huge bestsellers, yielding accolades that included two Booker prizes, stage and TV adaptations.

To me, Hilary was a calm voice at the end of an email, patiently telling me what I needed to hear. She became a beloved friend who I stayed in touch with for 15 years and saw occasionally in person. I treasured every moment I spent with her, always trying to absorb her wisdom between fits of giggles.

On Sunday 22 September it will be the autumnal equinox, and the second anniversary of Hilary’s death. While darkness and daylight are briefly balanced, here are the things I learned from her.

Know how your story ends and write towards it

A lot of ink has been spilled over whether creative writers should plan or “pants” their stories. Planners make meticulous notes before attempting a first draft. By contrast, improvisers who write “by the seat of their pants” jump straight in. Both approaches have their problems: overplanning is the equivalent to overthinking and the result is likely to be less organic; whereas “pantsing” can read as disorganised. Both methods can also create opportunities for excellence, through either a cohesive plot or serendipity.

A good third way is to know your ending. Hilary wrote the end of the final Thomas Cromwell instalment, The Mirror and the Light, “well ahead of time”. This is a simple method that creative writers can apply to their own work. Knowing how your story ends will serve as a compass, while leaving you with enough latitude to explore your imaginary world. And a crafted, impactful ending is ultimately more satisfying for the reader, too.

Write every day

I once asked Hilary if she wrote every day. “Yes,” she replied.

I felt slightly embarrassed at the time that I did not, but that changed when she gave me a week-to-view diary as a belated Christmas present. The spaces to write in were quite small, and although I had tried and failed to keep a diary on previous occasions, I decided that I could probably manage a line a day.

I learned that the best time for me to write in it is first thing in the morning with a cup of coffee. I note the salient details of yesterday, so I can mentally clear them away and feel more ready for today. I have written every day now for nearly seven years. I write a side of A4 daily, often around the margins, stopping when I run out of space. More than any published work, this benefits my wellbeing and keeps me honest as a writer.

Greatness and gentleness are possible

Hilary was a gentle person. She cared deeply about her readers and respected their intelligence. She nourished her readership with her storytelling, while still leaving them hungry for more: “Have I told them too much, have I spoon-fed them?” When she spoke to audiences at literary events, she transmitted her warmth to the back of the auditorium; and when they queued up for her to sign copies of her books, Hilary was delighted. She did not take their support for granted.

Throughout her career in turn, she supported dozens of other writers. Her endorsements adorn many book covers because she knew what a difference her star power could make. And it is indicative that when she was peak famous and I was least productive, with personal setbacks including breast cancer in my 30s (double mastectomy, chemotherapy, cancer-related fatigue), she showed me even more kindness. She reached out more often, still seeing me as a writer even when I could not see it for myself.

Hilary was also a cat person. The significance of family pets recurs in her writing, so I didn’t feel silly sending her pictures of my cat, more than once.

Back yourself

Hilary taught me there are two kinds of success for an artist: internal and external. Sometimes, these are at odds. The work we feel most passionate about is not necessarily the work that is most lucrative. Whichever mode you’re in as a writer – either being your own muse or hustling for a commission – believe. Have the courage of your convictions.

The quality of writing matters more than quantity

At about 900 pages, the length of The Mirror and the Light – the final book of the Wolf Hall trilogy – was a daunting prospect for some, and it prompted discussions about reader attention spans and stricter editing. This type of criticism underestimated not only Hilary’s enthusiastic readership, but also an essential ingredient of her brilliant prose: a clear, natural voice on the page. Hilary’s historical doorstops don’t feel laborious to her fans because every line flows and has intent.

One of my favourite pieces of hers, written more than two decades earlier, is Terminus. At a mere 1,690 words, Terminus is almost too short to be called a short story, yet it fulfils her creative purpose. Hilary’s writing was elegant. It was meant. It was exactly as long as it needed to be.

We don’t reproduce the past, we create it

Among the valuable materials Hilary has left for historical novelists after her are the BBC Radio 4 Reith Lectures. Broadcast in 2017, they are a compelling commentary on why we try to engage with the past and what is happening when we do. Hilary shares her strict adherence to historical facts; her frustration with the gaps in the historical record; and her preoccupation with French 18th-century drawing room wallpaper. She explains how familiar events from history can be transformed into surprising new dramas when a point of view is changed; and how the unknowns – what her characters think or feel – is where her creativity did its work. I won’t weigh in on whether historians are as inclined to “create” the past as authors of historical fiction. Anyone with skin in the game should refer to the recordings available on BBC Sounds and as transcripts.

Our best ideas have a timeline of their own

Hilary was in her 50s with numerous published books, essays and articles before she achieved “overnight” success. The Wolf Hall trilogy was her best work, but she also “couldn’t have written the books earlier”. She needed life experience and writing experience to do them justice.

New writers often ask me about the discipline required to write novels. What they imagine is being shackled to a laptop for a minimum number of hours a day, and days a week, until a target wordcount is reached. Recently, I have come to the view that it takes more discipline to withhold from a project until the appropriate moment. To trust and to wait. Sometimes family, health or career takes precedence. Sometimes the idea is too big and complex to tackle and you make several false starts. Sometimes the idea insists that the writer must mature enough first, before it can be written properly.

Hilary never got to read my finished second novel, Pathways. Seventeen years earlier as a far messier manuscript, with underdeveloped characters, naive themes and a completely different title, it was the reason we met.