"Current" in this sentence is like the flow of a river or a stream. To "swim against the current" means to swim upstream, opposite from where the water is going. "Carry along" is a little harder. Something else is moving, and you are moving without any effort because you are in or on the thing that is moving. If a stick is on top of a river, the river will carry it along; the stick doesn't have to do anything, it just moves forward with the river. To really understand the sentence, think of it like poetry. Life is like the river, and you can be quiet like the stick. I hope that helps!