Seems most of you stuck with the "bad" decisions long enough to learn from them and they didn't turn out to be career killers in the end.
My personal situation is that I went from "A" (5 yr) to "B" (1.5 yr) then back to "A" (6 months). 6 months ago, I felt, similar to SMS in the post above, that "B" just wasn't what I was cut out for.
My current problem is that now I think I was right the first time, and moving from "A" to "B" was a good choice for me.
"B" was a non-engineering role at an EPC firm, and I think I just let the ~evil~ engineers around me influence me too much. I looked around and saw my peers heading down the standard engineer career path and lost my nerve to do something different. I had a specific set of goals when I took the "B" position that involved ultimately having to leave the company for other opportunities, but I let the distraction of the career opportunites WITHIN the company get to me when I saw what my cohorts were doing.
Now that I've had a little time back on the engineering grind, I remember what I didn't like to begin with (drafters who need 3 chances to pick up red marks correctly, construction dictating design, a boss who reassigns people working for you 4 times in 6 weeks, working OT to meet schedule just to be working on the same thing over and over and over again for 6 months because of infinite client changes, spending precious hours of my life discussing whether stub-in or stub-out branch connections are okay instead of fittings when I really could care less about branch connections). Still, I feel like I need to give it more time and not run back to my old boss like an idiot and beg for my job (there's an opening), but I also feel like it could be a waste of my time to keep doing something I don't see working out long-term. . . except for it does build character, as some of you mentioned. Do engineers need more character? I personally got all the character I'll ever need being on the math team and in band in junior high ; )
On a serious note, if I did stick it out for another 6-12 months and still feel the same way, any opinions if it be reasonable at that point to talk about going back to "B" with the two bosses involved, when there was the next opening and I could finish up my current projects? I will have my year-end review at the end of the year (duh), and I don't feel that saying "Everything is GREAT!" is the best choice if I really feel on the fence about the job.
Thanks for sharing your stories and advice.