Moving Up the Corporate Ladder

I'm totally stressed out lately. I have a major work dilemma. Never in my life have I ever had to quit a job because I had options. Usually I was being let go because of a merger or I had to leave because I was going away to college. You know, there were outside factors leading to my change in jobs. But I never left a job because I could. Well, that's my dilemma.

A former co-worker has offered me a position to work with her. She's in charge of way too many departments at the new place and needs help. This would normally be an easy decision but the problem is that I've begun to like my job and I really like my boss. There's a good bit of convenience since there is an office for me to work in across the street. Plus, it took a while to finally feel comfortable at my job and I would hate to uproot and try to fit into a new place. Yes, change scares me.

So that's my dilemma and I don't know what I want to do. I don't want to pass up a can't miss opportunity but I also feel like I'm not done with my current job yet.