One of the biggest obsticles I faced when working out, is that I gave up half way through the workout or didnt start the workout at all. Why, because I couldnt produce self-motivation. I tried anything to keep doing my workouts. I played high bpm music to get a good rythm, I would record my progress, I would look at myself in the mirror to feel that motivation and it just didnt work for me, but one thing did. I would tell my friends to try the routines themselves or with me. They would come over to my house to workout or I would give them a copy of the workout but course I wanted to do better than them. I would do more reps, add more weight and other things that would show I was "better" than them and to improve faster. It payed off, I would complete the routine and even add a little extra. I got faster and better results and now its easier to commit to the next challange.
Thats one of the biggest piece of advice I can give you guys. Make a bet with a friend. Tell everybody you know that you started an exercise routine. Challange other people to start the same program. When you go to the gym invite people to go with you. All of this will keep you motivated and can give you a little extra on your routines. Telling people that you have started a new exercise program puts you in the best motivational position, because if you follow through they will be impressed and will make them follow the same program due to the awesome results you got, but if you quit and fail they wont stop making fun of you and call you a quitter. Making a bet is great because extra money on the wallet wouldnt hurt. Challenging people into trying the same program is an excellent idea because of the results. If you see that your friend is getting better and faster results, you will feel motivated to do better than what he's doing. Inviting people to the gym proves how the mind is the biggest tool ever. Your mind will analyze how your friend is doing if you see that hes doing better than you, you will want to catch up to him. If hes doing worst you will want to show off and leave him behind.
There are many other things that can keep you motivated but self-motivation is the best. Adding those useful things to your routines will easily improve your results.