As an addition to what Jake said, Rick also has explained it to me in terms of flying an airplane. A little airplane is flying at 100 mph through the air. If it has a 25 mph tailwind, it is not flying at 125 mph and if it has a 25 mph headwind, it is not flying at 75 mph. It is always flying at 100 mph through the air. It is only in relation to the ground below that it is traveling at a different speed. So if you have a tailwind you are going to get to your destination faster and if you have a headwind, you are going to get there later.

In terms of time, if you are in the air for an hour, you will burn the same amount of fuel whether you have a headwind or a tailwind. But if you run out of fuel because of a headwind, you may end up crashing on the side of a mountain. In the case of a sailboat that runs out of wind (your fuel), you may end up crashing on the rocks on the side of a channel.

A sailboat has one option available to it that an airplane does not. A sailboat can throw out an anchor (if in shallow enough water for your length of rode), and wait for more favorable conditions.

When I was trying to get up that channel against the wind and current, I kept thinking, "I wish I had an anchor."