My boyfriend is a martial arts and kickboxing instructor and this is one of his favorite phrases. When he's talking to people who come to his class and work hard for a few weeks only to get frustrated by their lack of immediate progress, he gives them this speech. "40 miles into the woods; 40 miles out. It took you how long to get out of shape? Probably years. Don't expect to get yourself into shape in a few weeks."
One of my personal favorite phrases is a quote from Aristotle. "We are what we repeatedly do. Excellence, then, is not an act, but a habit." So too with fitness. We can't make an epic effort for a short period of time and be fit. We have to make a sustainable effort for a long period of time. We have to be consistent. Our bodies and health will reflect our long term habits.
So don't give up if you're only 5 miles along on your trip out of the woods. Keep going. You'll get there.