I'm a strong believer that you have to confront negative thoughts and resolve underlying issues as soon as they arise and not neglect them and tell yourself that everything is going to be OK. It's not going to be OK. Murphy's law; what can go wrong WILL go wrong. This has been shown to me over and over again. You cannot leave anything to chance.
I'd rather have a few negative thoughts from time to time and resolve them as they come than fool myself into thinking that I'm living in la-la land and then after a few years find out that it has become hell on earth due to my neglect.
It's like a garden; you need to maintain it. If you ignore the weeds, they'll eventually take over your garden. You can tell yourself that the weeds add charm and make your garden look more natural; that you're going for a "wild tropical look" or whatever, all part of the plan, but with that attitude, you're bound to fail. You'll just keep getting more of whatever it is that you neglect until it becomes unbearable.