This.

Nonintuitively, the best way to stay warm enough is to not wear too much -- most people wear way too much. Another thing to keep in mind that you shouldn't try to be comfortable at all points on the ride. You should feel chilly for the first few miles, on extended descents, and the like. If you try to make yourself warm everywhere, you'll never be happy. Obviously, if temps are expected to drop, you should carry something for that.

I like riding in the cold, but the snot has always just flowed. Just perfect your snot rocket technique and you'll be fine.