No one system fits everybody. The important thing is to keep trying stuff. I did martial arts as a kid. Pretty good but after 3 schools with all 3 heads of schools being psychos I gave it up. Tried the gym, boxing, tennis, yoga, etc. but getting into a regular routine is tough. Something always comes up, gets in the way, instructors move on.
The things that really worked for me;
1. Tai-bo. The Zumba of the early 00's it's basically aerobics mixed with boxing and martial arts moves. The main reason I liked it is because I could already do the martial arts and the side kicks really toned my waist right down when nothing except running did before. Being able to just follow a video/DVD along means I don't have to go anyway or think too hard about it.
2. Getting up early and doing it. Motivating yourself to do it is hard but I got around that by making myself get up at 6am, changing into a pair of shorts and then starting the tai-bo DVD while I'm still half-asleep. I'd just keep telling myself the mantra over and over in my head. I'm going to feel alot better in 10 minutes and I know I feel really energised for the rest of the day if I do this. So that would get me through those 5 minutes where my brain wants to say 'no'
The main rules to remember when attempting to achieve any goal;
1. You must believe behaviour A (exercise) will led to goal B (feeling healthy). Have a goal in mind and if you truly believe doing behaviour A will get you goal B, and you really want goal B, then you will have the "will power", because that's all will power is.
2. Baby steps - Don't over do it. Everybody wants the best rewards in the quickest time. It doesn't work like that. Do a little bit each day, make it part of your normal daily routine and it will no longer feel like "extra work" and the changes will happen in due course.
Good luck.