[Mojo]

I would have to say Love, closely followed by Dreams and Hope, which amount to the same thing in my opinion.

If you have nothing else, but you have love, that should be enough. On the other hand, love can inspire hope and dreams....

I reckon love, simply from experience - almost everything I do is due to love on one level or another. Also, knowing you're loved is surely the only reason you need to stay alive.