So much fun, you have to be ready for it.
I think the key to handling a backpacking trek is to always be generally active. Walk, run, bike, skateboard, roller skate —- whatever. Our bodies are made to move, and we need to keep them moving. I hear they tend to last longer and perform better that way, AND you’re more ready to take on that backpacking trek that comes up now and then without having to put a lot of time into getting in shape.
You can spend that time instead on figuring out how to make sure you have what you’ll need and still be able to carry that monster of a pack on your back. Those things are heavy.