You use "I'm trying to ___" to describe something that you want to do, but isn't easy.

For example:

I try not go visit Facebook too often.

This means that, in general, you don't go to Facebook.com – maybe because you think it's a waste of time. On the other hand:

I'm trying not to go on Facebook too much.

This sounds like you want to stop going to the site, but it's difficult for you to stop.