I almost ALWAYS feel this way as well.Some days I hate the world and just want to give up and some days I am full of plans and life.The thing I figured out was just to live life anyways,in spite of such extreme mood shifts just as long as I realize the consequences of my choices.I used to do alot of stupid and careless things to get a rush or when really depressed.I now try to objectify the moods and just get through them..I have gone through many lol.