Raft is really just to teach you how to use the sailing mechanic. It is really not a good way to actually travel with. Walking is faster.

That said, you can actually still sail even when the wind seems to go "against" you. Just try it. The raft/boat may act weird, but that is how it goes in real life. This is how you learn how to sail.

Also, you can row. Just try the movement keys (Usually WASD) and you will figure it out quickly.