That's called anxiety. I dealt with the same thing. You've built up art in your head as this big thing, this big achievement that you're gonna go for and now it's too much. All this pressure makes it seem like an insurmountable task, and so you keep putting it off.
What you need to do is realize that starting anything isn't easy. It will feel clumsy and forced at first. It will be unpleasant. But let's say you expose yourself to that unpleasantness of practice for an hour a day. Whew that wasn't so bad. Then the next day, you do it again. At some point, you're going to build momentum. You're going to start learning and getting better each day. That's when that good dopamine hits you, as the process of practice, hard work, and improvement become a reward loop for you that can keep you going. Before you know it, you will be addicted.
Keep in mind that there will be road blocks. This usually means that you don't know the way to proceed. It can happen when you're learning on your own, and there's no one there to tell you how to learn. Well, that's what you have this place for. Here you can ask people how to proceed, what to learn next, where your gaps in knowledge are that can help you move on.
But you have to get started. Break down this huge huge endeavor into small steps. One step at a time, chip away at it. Learn a little bit each day. Set a minimum amount of time for practice. You don't have to become a pro in one day. But you can start drawing little things, boxes, spheres, those loomis practice heads, and so on. And that little bit of practice will add up eventually.