Most of life is cyclical if you slow down enough to look at it. Most of us understand these words pretty well, because they govern that cycle of life. Maybe you've dieted before. Maybe you lost weight. But here you are, heavier than where you were before, maybe even before you started your journey.
For a lot of things in life, we seem to get obsessed with it, if it comes into our life. The idea of getting fit takes us over, and we become obsessed. It's our main focus, day and night. Until whenever that day comes that we “fall off the wagon”. Why is that?
Here's the thing, life-consuming concepts such as fitness all day cannot be sustainable for long periods of time. Diet and physical stress especially. So when that time does come, that we can no longer constantly think about our next meal, or our next workout session, we bail. We “fall off the wagon”. We're just not involved at all anymore. “I'll start over next Monday”.
Instead of falling into this cyclical pattern, ease into it. Find things that help keep you balanced. Whats sustainable for others may not work for you, but most people can eat a decent diet, workout a fair amount, and rest a good amount. The problem is how we build our program around obsession. Working out constantly. “I'll get 4 hours of sleep if I have to! I can do that until this is done.”
So instead of all or nothing, incorporate fitness/health, or whatever thing your coming across into your life, don't let it become your life. Don't obsess so much you become uninvolved entirely, especially if it's good for you.