So - when I was about 13, I was really into martial arts... specifically, ninjas. Like, way into them - as in, I had non-lethal weapons and pictures of target points on the body hanging on my wall. Quite frankly, it was a good thing that I didn't have many (read: any) girls that came into that room, because it certainly wouldn't have helped my cool factor.
But I digress.
One of the stories that often came up when I read about the ninja was about their training regimen. Amongst other things, when the trainee was a child, they would plant a corn seed. Every day, they would jump over the corn seed 100 times. Now, corn grows quickly, so they would have to jump higher and higher - but from one day to another, it wasn't a hugely noticeable difference. But from week to week, month to month - it would go from inches to feet. Once they reached a height that they failed to clear 100 times - they had to plant another corn seed and start all over again.
This, at it's heart, is what can make your training successful. Now, I'm not suggesting you limit your training quite this much - I mean, we need to have fun as well - but you should dedicate a certain percentage of your fitness training time to dedicated practice of all your basic skills. If you are constantly changing what you're working on, you never build any sort of foundation and never really progress - like a hamster on a wheel. Frankly, this sort of dedicated practice is exactly what will make other activities more fun - because you're building the foundation elsewhere for success.