Why can't I close my own questions ? I should be able to close it once while I have either received an answer or I find the question was either too broad or whatever
Just because you are satisfied with an answer that the question has received, that's no reason to close it. If you accept the best answer, that marks the question as having been satisfactorily answered, so people know that you don't still need an answer. But if the question is clear, on-topic, well-scoped, objective and unique, it should be left open, so new and better answers can be added later, and future searchers can benefit.