You should look at yourself as a glass of water and see the people in your life as plants.  You have to be wise and selective about who you provide water for growth, remembering that weeds often pose as flowers. Regardless of whether or not you see the glass as half empty or half full, you have to sustain water for yourself for survival.
There has to come a point in your life where saving yourself becomes a priority over saving someone else. When you make a decision not to save someone, it has nothing to do with “not caring,” but it is about coming to the realization that everyone that bleeds, doesn’t need saving.