First of all, don't try positive thinking. Positive thinking causes more harm if you're not positive to start with, and most of it's bullshit anyway.
Second of all, as ridiculous as this sounds, you don't need a reason to continue living. It's not as if you always need something to strive towards, to "live for". Things change, who knows, you'll eventually find something.
And lastly, don't even think about suicide. Suicide is one of the most selfish and harmful things you can do, not to yourself, but to those around you. It leaves your family scarred and empty, likely more so that you are now. But if you're the type that will want to just so they will cry about you and reminisce and regret not "treating you better", then you're a dickhead and don't even deserve them.
Not saying you are, though.