When we exchange marital vows, we promise to support one another in 'sickness and in health'. A mother makes no such promise when she gives birth. Yet it was, and is, you who has born much of the brunt of supporting and looking after me 'in sickness' when I am struck down with depression.
It all began 17 years ago when I suffered my first major depressive episode. It wasn't that my darling husband didn't want to help: he did his very best. But he was also trying to hold down a job in financial services where he worked long hours and often travelled. It was you who lived nearby and who could come and spend the day with me.
During the acute phase of the illness I was bed-ridden, unable even to get to the bathroom without your help. I remember you telling me that I couldn't be left alone: I had a sense that I was falling, the bed was falling, as if I was hurtling downwards on a crashing plane which never landed. I would grip your hand or arm, which soon turned a livid red. I was literally hanging on for dear life, every muscle tensed, every sense alert, fibre strained, cell taut as I lay clenched in the foetal position trying to hang on. All I could say was "I'm going to crash!".
In response you took to reciting a phrase from the Bible: "My grace is sufficient for thee; my strength is made perfect in weakness". This was a different, more positive mantra than my previous chant. Very gradually, I began to repeat the line with you. There was some point to the illness. My strength would indeed become perfect in weakness.
Gradually as I began to get better, you would read aloud longer passages and poems to me as you had done when I was a child. You had always kept a commonplace book of snippets of poetry, prayer and anecdotes that had particularly struck you, entitled 'Consolations'. I devoured the collection as if it were ice-cold water offered to a parched traveller.
Some mothers and daughters are bound by a shared love of baking; others bond over their enthusiasm for a particular television show. We had always been united by a love of poetry. When I was a child, you had furnished me with several gorgeous illustrated anthologies.
Now poetry proved the perfect medium for me when I was ill. For a start I wasn't well enough to listen to, let alone read, anything longer than a few verses. So poetry's brevity was a blessing. So too was the way it dissolved the feeling of solitude. As you read poems such as 'The Flower' by George Herbert, with its line 'Who would have thought my shriveled heart / Could have recovered greenness?' I realised I wasn't alone and others had made something of their suffering.
Then, as my recovery gathered pace, it was you who accompanied me on my first trip to the post-box and back; then to the café at the end of the street; and on visits to my psychiatrist and the hospital.
Caring for someone with clinical depression is no different to caring to someone with any other serious illness. There are doctors' visits to arrange; beds to be made; trays to be brought upstairs; sheets to be changed and smoothed. All this you did.
And then there is a household to run and children to care for. This too you did. All the while, unbeknownst to me, it was you who had been unloading the dishwasher and emptying the washing machine; filling the supermarket trolley and putting our children to bed. Such was the ferocity of the illness that I had been utterly absorbed in my own battle to survive and had been unaware of the household continuing around me, directed by you.
Even now that the acute phase of the illness has passed, and I have learnt to manage my Black Dog, you are still a crucial source of support. You can spot an edge to my voice and a familiar frightened look in my eye. You are the one to tell me to slow down and look after myself: feeling overwhelmed is a sure sign my depression is not far behind.
Much as I still rely on you, I know that I must learn to do so less. You are now in your late seventies. It is for me to care for you, just as you have looked after me for so many years. It will be a tiny token of thanks after all you've done for me. I hope I don't break this promise.
Rachel Kelly's memoir, Black Rainbow: how words healed me - my journey through depression, is published by Hodder & Stoughton and is available for purchase on Amazon. The Black Rainbow app can be downloaded for free on the Apple App store and on the Google App store for £1.49. All author proceeds to SANE and United Response.
Rachel is running a series of workshops on the Healing Power of Poetry at the Idler Academy, 81 Westbourne Park Rd W25QH, every Wednesday 6.45-8.15pm from 5th-26th November. Visit the Idler Academy website to sign up.
Follow Rachel @rache_Kelly or visit www.blackrainbow.org.uk