If the problem is really that you have such an overabundance of possible topics that you can't possibly choose, then I think it would be helpful for you to list some of them -- along with a sentence or two describing what you'd argue or explore concerning each one. Then people here might be able to tell you what sounds most interesting or potentially fruitful. We don't know your background (psychology is a big field, to put it mildly) or interests -- without some indication of those, this has more the feel of a fishing expedition.