I completely understand what you are going through. This workflow takes a lot of practice to get good at. I’m still very much learning a lot of it myself. But I’ve been at it for about a year now and it really shows compared to my early work. And once you get the hang of zbrush and substance painter you can really do cool stuff in very little time which is in turn very rewarding and keeps you motivated to make more. 
Good luck with your project. If you have any more questions, don’t be shy to ask. 