I take this phrase that I liked a lot.
Think big, start small but be quick.
I am one of those who are struggling with the idea of staying motivated, because it really is not easy at all, there are many factors and circumstances that make it very difficult to keep motivation. But the answer is as you mentioned it, to establish a goal, especially since you always have to know where you are going when you want to undertake whatever you want to do.
I understand you, friend. I've been through a lot of these times and I'm still going to write a lot about entrepreneurship. I can say that maybe some people misunderstand some posts that I will still do. But to succeed we have to learn to listen to what we do not want and people always want to hear what they want. Regards. Success!