Fitness reflects one’s suitability for purpose, and doesn’t just refer to one’s physical conditioning, though that’s certainly a part of it.
Just as with physical fitness, moral fitness is an ongoing endeavor.
The good news is that, if you start off badly enough, it’s a lot easier to make improvements.
It’s sort of like a couch potato — he can get impressive gains of strength in the gym in just a very short time, because most of what he is doing is neuromuscular recruitment — basically, learning to use the strength he already has. But a guy who is already squating twice his bodyweight and at 10% bodyfat will only make incremental improvements.
The moral equivalent of a couch potato can make quick improvements with some low-hanging fruit. But making moral improvements becomes harder over time.
Every day is a good day to commit oneself to being better, in some way, than he was the day before.