That's me in a nutshell.
I like my job, but I've found myself in an organization where the sky's the limit. There's plenty of ways to move up if I would just get in with the right crowd. So far, I haven't found a way to do that considering a) I don't like to work overtime unless I have to, and b) I lack self-confidence to insert myself where I'll get noticed. So, instead, I enjoy a modicum of success, but in my head, it's never enough. I get insanely jealous of younger colleagues who are supremely ambitious and somehow have all the upper management wrapped around their little fingers while simultaneously pissing off their peers. And I'm horrible at hiding the green monster.
Some days, I'm ok hanging out at the level I am now for a few years and getting some good projects under my belt. Why not? It's a great position to be in. Interesting technical stuff, big projects to manage, and relatively little headache compared to what higher positions bring.
Other days, I'm irritated with myself for not doing MORE. Not publishing papers, not being more involved in professional societies, not networking. When it comes down to it, I won't be happy staying in the position I'm in for the rest of my career. I have to constantly be striving for a higher position.
Notice a trend? I have a really hard time staying in the present. The plans of the future are continually popping up. Trying to stay present, to focus on the here and now, not what I think should happen in 5 years is a huge problem.
And, why can't I be happy in my current position? It's a good one!