Lithium works best in people with text book Bipolar I--euphoric manias, severe depressions, very little (or no) psychosis, good functioning between episodes. Even then, the stuff is potentially dangerous and often not easy to tolerate. Low(ish) doses are sometimes used in recurrent episodes of depression (no bipolar) and/or in "Treatment resistant depression," but I don't think that's a very popular strategy these days.

Maybe its just not for you? could be a blessing in disguise. You might do better on something more modern, safer, "cleaner," etc. Lamictal, trileptal, keppra, etc. etc. etc.