Some people have no sense of emotional self preservation. They keep getting involved in the same situations and with the same types of people. Then when the same painful results happen, they can't seem to figure out why "it happened again."
A monkey poking a termite mound looking for food will only poke for so long before its sense of self preservation kicks in and says "hey there is nothing here. I am wasting my energy. I need to stop doing this and try something else."
But there are some people who don't have that part of themselves. Some tend to ignore it because they realize they have invested so much energy into that person or situation, that to stop would mean having to admit they made a mistake.
Some are so dead set on getting what they want, that the thought of it not being found with said person or in said situation is not a acceptable answer. They will keep poking at it until they get what they want. Even if everyone around them tells them it's not there.
It isn't what they want to hear, so the keep plugging away at it. Then they wonder why they keep getting hurt.
You have common sense for a reason. Use it.
And as for the enevitable cliche' "Common sense isn't common", that isn't true. It's the use of common sense that isn't common.
Stop complaining about the same thing day after day. Month after month.If it's bad enough to complain about, then it is bad enough to take action to change the situation.