I love a girl, but i know we will not be happy together, what should i do?

i don't know whether she loves me or not.But she definitely likes me. But we are very different in our ways of thinking and dealings. i am more idealistic and classic kind of guy and she is practical, care-free girl. i think a lot and she does things on the go. This makes me think that we would not be suitable for each other. But i love her. And she knows it that i love her. What should i do?