i dont understand

i just dont understand where my life is heading... or even where i want it to go.
this morning, i felt fine, even happy. but now im uber-depressed, and i dont really know why. a number of factors...
jeezzz.
why do the ones you love hurt you? and cant we just shut ourselves out so we dont get hurt?
last yr this time, i mustve been really happy.
last 2 years this time, i mustve been more than really happy.
these mood swings suck...