I recently stumbled across this advert on youtube, after originally seeing it quite sometime ago.
It contains a very short but to the point insight into training motivation which I find speaks to me.
Even if you are not exercising to be better at a particular sport, I think that this message can be applied.
We are all exercising for some reason, maybe to be healthier or look better or gain confidence. Whatever it is, there will be those moments that test your progress, and when you come across those moments don't you want to honestly be able to say to yourself: "I tried as hard as I possibly could".
You make dozens of choices everyday which will effect your ability to reach your goals. You have the power to do what it takes to bring yourself closer to realising your full potential or set yourself back further.
Generally I find that people pretty much know what they should be doing to make themselves healthier, the problem is that they make the wrong choices, time and again.
If you want to do something, you can do it! Don't listen to the nay-sayers.
However, you are going to have to stay focused, I find that messages like the video above keep me focused and help me to make all those little choices that when you add them together, make the difference between me and the next guy.
Train hard, live happy