[mvdgaag]

I think your memory of your experiences may be biased. It is very easy to remember all the times you get action against a set and forget the top pairs where someone had a better hand. Use a program like poker office or poker tracker and see how many of your sets got action and why. Your leak may be overplaying your hands.

Also you might play big hands wrong. If you hit a set on a 5s6s9d board someone might easily outdraw you if you think you should play it slow (like very many players do). While if you hit top pair you will probably not give them the odds to draw. There is as much reason to protect a set against a straight or flush as there is for one or two pair, because they'll all lose against these hands.

I don't know any specifics about your game, so the only thing I can advise is to review the hands and see if you were just unlucky to face a better hand or playing it wrongly.

GL