Lucky you. Since I've been up that mountain, I can tell you. And if I'm lucky, maybe remembering will help me get up the next goddamn mountain. (Sometimes, life seems like a series of goddamn mountains. But you don't climb them because they're there. You climb them because you are.)
There are three things I've found that have gotten me started, and have kept me going. The first is cold, unemotional reason. First you need to choose a goal that's a little more reasonable than winning the lottery or sprouting wings and becoming the first winged asshole to circle the sun. You have to do something that's doable. And fuck the Beatles if they don't like it. I don't give a shit if there's nothing you can do that can't be done. There's plenty that can be done but hasn't been, because some lazy hippy fuck hasn't gotten up off his ass to do it. The "doneness" of stuff isn't some irrelevant characteristic of entities in the universe. Shit doesn't just "happen". Shit happens because someone thought of the shit and figured out how to make it happen.
Once you've got the shit, and once you've got the plan, you still might not feel like lacing up your sneakers and running the 26 miles. But hey, you're the bastard who decided to run the marathon. So who the fuck cares whether you feel like it or not? You need to keep the shit, the plan, and the knowledge that the shit can be done in your conscious awareness. Since I'm a big fan not only of mixing metaphors, but also of running them into the ground, let's call the knowledge of your plan the engine. Emotions are only the fuel. You might be able to get a decent high from gasoline fumes, but without an engine you're eventually going to pass out in the same spot where you started. And the guy who wins the race is going to have a slightly more respectable smile on his face than that gasoline-smelling son of a bitch asleep at the starting line. (You're paying attention, right? This is a car race now, not a marathon.)
So to throw another wrench into the pit stop of achievement metaphors, let's say that rational thought is the first building block of achievement. Reason, not emotion, gets you started.