I've tried positive thinking and things didn't turn out right..

I think your heading the the discussion shows that you do not look at the positive side fully, specially when you say - things did not turn out right. In my opinion things would have come right, but not to your expectation. I believe therei is positivity in every happening, it is for us to catch it. Coming back to your discussion, I just do not tell myself that I cannot do it. I always feel, that I can do it and I should do it sooner than later.

I used to have a really bad outlook on life for some reason. I used to think that I was no good at anything so I never tried anything and just said "I can't". Turns out that I can. It's amazing how if you let your guard down for just a minute you can do almost anything you try...even those things you thought you couldn't do. I try a lot more now because I don't worry about the failure risk. If I can't do it at least I have the chance to say that I tried. And saying that you tried feels so much better than saying that you couldn't. Hope this helps you out.