K's are the type of hand you can find yourself broke with, or you can take down a pretty good size pot with.
You should definitely raise pre-flop with them (to eliminate opponents with weak A's) to narrow the field. If you're re-raised, or worse re-raised all-in, it' s nearly impossible to get away from the hand. However, unless you're 100% certain your opponent has A's, you have to throw your money in and take your chances.
I've lost my fair share of hands with K's, but have won quite a few big pots with them as well. There's nothing more fulfilling than having them, getting a re-raise from your opponent all-in, you calling, and finding out they have Q's or middle pair. You got your money in with the best of it, and that's ultimately the objective to be a winning poker player.