Why do people allow a situation that doesn't bring happiness to them to be a part of their life?

Well there's two different answers to this. the first being, that most don't allow hard things to happen. They just happen. But in doing so, they teach that person a lesson, and what doesn't kill them only makes them stronger. It may hurt down the line, and take time to get over, but a lesson learned is one of the best. The second being that the person just plain doesn't care anymore. This said person may have went though so much during their life they've lost the spirit in them to fight against the hard things and try to keep the happiness in their life. No matter what you go though, don't lost that spirit. Any time you're having a hard time, just go to the lord in prayer and give it to him. And I know that might be hard because you want to deal with it on your own, but trust me, sometimes the best thing to do is to let the lord have it.