I like to consider myself a realist. My mother is very pessimistic, and I have allowed myself to be talked out of a lot of things, including jobs, promotions, moving, etc. At some point in my life, I was very pessimistic too, and I didn't try a lot of things I wish I would have.
However, I have this tendency to get something in my head and go with it, but to my mother's dismay. I went away to school against her wishes. I changed majors against her wishes. I took jobs that she didn't want me to take. I work in a traditionally male only field, and she hates this. I do it though against her backdrop of pessimistic talk, and I find myself feeling very guilty. I don't consider how I feel, or how good the change will be for me, all I consider is her feelings, thoughts, and desires. I'm planning to move out of her house and into my own place. I have very good reasons for doing this that have absolutely nothing to do with her. When she found out that I was considering this, she immediately started in with, you'll never be able to make it on your own, you'll have x expenses, you need to think about this. You're going to take your son out of a stable home environment and he's going to regress even more.
Sometimes, I find it very hard to turn off the mantra of her voice in my head. I have heard for the last ten years that I will never be able to make it on my own, but I think I can. I even wrote up a budget that says I can, without ever dipping into my savings except to buy things I'll need. Granted, we'll have to be a little frugal, but that's all right too. I have this desire to prove my mom wrong all the time. I suppose it's a sort of rebellion. She would say I can't, and I would try to prove her wrong.
So, I consider myself a realist. It's nice to be optimistic, but we have to face the realities of our situation too. That's what I try to do.