Bobbyk,
i don't think that taking the odd leftover tablet is likely (in general although there are exceptrions) to hurt but nor is it actually likely to solve your problem.
Mood swings - food, lack of exercise (or inappropriate exercise), doing or watching or reading things that depress you (so do, watch read things that don't upset you).
Aside from the above some solutions : ces machine dynamind.Com sound & light machine dynamind.Com, cbt, natural supplements like 5htp, valerian, sam-e, dhea, gingko, st johns wort.