I've sailed more or less continuously since I was 14 (now 40), so I've never actually quit, but I did slow down a lot.
For a while there I got too fat for my kit

(old school pin tail waveboard), and every time I went out I ended up grovelling around and came home frustrated. A few seasons went by where I only got out half a dozen times.
The catalyst for me was the GPS Teams Challenge. Bought some slalom gear that was more appropriately sized (115L board + 7.5 cammed sail), got the GPS bug and my TOW has gone up massively.
Now I've got a shed full of kit to cover all conditions, I've dropped weight and I'm sailing as much as I was when I was 18.

Helps that I have flexible work hours (I'm in consulting) and a lot of autonomy at work. An understanding wife also goes a long way (I've got three boys under 6).
It's a fantastic sport. The exhilaration can't be beat. Now my eldest boy wants to have a crack, and hopefully the other two will as well, so it's very much engrained in my life. Certainly helps maintain that work-life balance...ain't too many workaholic windsurfers around!