A lot of people blame their lack of success in how little motivation, thinking that maybe success came easy for a lot of people, or leaving things for later wishing they would get done in the blink of an eye, making everything else so much easier.
As humans we connect feelings and mental states to our work. A lot of authors have written their best novels when tragedies happened in their life, or they were happy about something, reflecting their emotions into their work, making it a lot better than before.
But what happens when those emotions start to conflict with our work? That's when having discipline becomes important and a priority.
It all becomes a vicious circle as you'll find excuses to not do something, you think that in order to do something you have to get there first, when in reality you must work to get there and keep working. There aren't any shortcuts and even if there were, you would never feel the same way as if you've worked to get there.
The key here is to start, you can always wait around to have the perfect mood to start that task, but you'll never know when that will come or if when it comes it will still be worthy, and that energy and mood will not run forever, at some point your hormones are going to have a break, and what happens then?
In order to succeed you must try different things, see what you are good at, see what fulfills you, worst comes to worst as you may succeed in something you hate, which you can change. But at least you proved yourself you can do whatever you want, you just have to be disciplined enough.
And all of this comes from building habits, good ones that will help you do more of those things you have to do instead of doing what you feel like doing. The difference between the two of them it's ginormous.
Always go with discipline, it will take you a long way. If it fails the first time, keep trying. If it isn't for you, at least you tried it. It doesn't have to feel good as you are doing it, but once you are done, it'll sure feel good.