I broke my back 5 years ago after my mare had a huge bronching episode and launched me in the air. Till then I'd had no confidence issues and had sat her bucks many times, I used to laugh about it, suddenly it wasn't funny any more. I didn't ride for the next 3 years and had no offers for anyone to exersise my horse (not surprisingly). About a year ago I realised that not riding had left a huge gap in my life, I went for some lessons on a very safe school horse then set about trying to pretty much re break my girl, no one had sat on her for 3 years. I had no intentions of letting her go and couldn't afford another so she was all I had. I was scared, very scared, but we took it slow and I tried to remember what it felt like to ride all those years ago and I remembered the laughing, so I did just that, laughed, every time I felt scared I made myself laugh. It was hard at first but it really helped.
To sum up I'd say remember what it used to feel like, not what you did, I wont ever do the crazy things I did 15 years ago but I can walk and trot round and laugh and enjoy myself, I don't need to do the crazy things anymore so don't put too much pressure on yourself and it will take as long as it takes.