What good replies
I have to take Spydertek's slant and say, while good responses, the real question that I saw was what STOPS you from diving, not what PREVENTS you from diving. And, I think that at the top of my list is one doesn't find it fun anymore for whatever reason: burn out due to one too many classes or not enough "me" time, an ongoing bad experience with the LDS, some bad experiences u/w, etc. etc.
As far as preventing me from diving:
1. Money.
2. Time.
3. I'm with Ber Rabbit on this: I work nights, have some mixed weekdays off (for some reason my buds don't get to take off work to go diving).
4. Location; have to drive a couple of hours or more to get to a decent dive hole.
5. Any of a number of ailments: ear infection, sinus colds, stomach issues, etc.
6. Any number of weather or environmental factors: 6-10 foot waves, rainy and cold (just a miserable experience), gut feeling, etc.
And, I must say Fishkiller: 60 degrees F is quite a warm day of diving; I'd be happy to dive in that temperature any time. Most of the dives up here in the :cold: north are under 50.