Get positive. It's pretty hard to get anything done when we're stuck on thoughts like, "Ugh, life sucks and it's raining." Thoughts like those make us want to just curl up in our beds until someone physically drags us out. You can't do that! Positive thoughts are the only way you'll even find motivation in the first place.
If you find yourself thinking negative thoughts, just stop. Don't finish it. Divert your attention elsewhere. Especially if you're thinking about your motivation! This task in front of you? It's totally doable and you have the abilities to do it. Any other thinking will keep you from even trying.