I've fallen into this trap before.
I play tanks. Prior to playing tanks (end of BC and forward), I played a healer(early BC). Prior to that, I played a dps (all of vanilla).
Why all the switching? Well, I saw a need, and jumped up to fill it. I had a decently fun time playing my rogue in Vanilla, but got burned out on the raiding scene right about the time my guild was a good ways into AQ 40. I took it easy and just chilled until BC released, where a group of friends and co workers all decided that we would make our own guild. We had a tank, we had dps. We had no healer, so I created my paladin and healed my fruity elf cheeks all the way through the first raid dungeon, where guild problems and frankly just lack of skill by the rest of the group stalled us out.
What is the end result? I loathe healing.
The guild stopped playing and most everyone quit. I decided I wanted to start playing again for the wrath release, and the rest of the guild sorta followed suit. Except this time, I wanted a tank. So I made a death knight and leveled it up 80. The only other tank we could find as a guild also happened to be a death knight. I didn't think this would be the best raid make up for the group, and we didn't have any other tanks, on top of me not completely understanding the mechanics of DK tanking at the time led to me once again dusting off my paladin.
The guild was actually successful this time, and we had accomplished all of the current raid content that was available prior to Ulduar. Right before that, though, I once again got completely burned out on my paladin. Guild drama ensued and the group fell apart once again, and I stopped playing.
A few months go by and I think it would be fun to play the game with my wife, and actually get her through the two expansions we paid for, but she never saw.
This time around, though, I resolved to play what I wanted, and be more relaxed about everything. And it worked, too.
I'm happy as a clam now, on my new server. I have a good group of people that are doing weekly 10 man raids, and I get to play my death knight tank, which I am really, really enjoying playing.
I'm in a role I enjoy, playing the class I enjoy, and doing content that is enjoyable and challenging, with my wife!
The moral of the story is, find the class you like, find the role you like, and stick to it. There's a lot to accomplish in warcraft, and finding the right character can help you stay happy and motivated in the game. And beyond that choice, find a guild where the people share your goals.
And just for fun, here's Soul and his new buddy.