My University counselor has been trying to get me to think more positively recently, and I admit it is a bit annoying.
I will say that positive thinking is not a solution, but sometimes when you're thinking negatively, you can talk yourself out of very real solutions.
Positive thinking is not going to help you in a situation of crisis, but you might be reluctant to call Lifeline, because you might have negative thoughts about it. You might have to wait a long time, or you've heard some horror stories about it or whatever. In THOSE situations, I would say that you have to think positively, or at least give it a chance.
I've said this before, but when you're meeting new people, give them a blank slate. People may have hurt you before, but the people in front of you aren't THOSE people. If you think negatively, you're not going to give them a chance.
In the end, like everything, it's complicated.