One think that I could understand to the time - there are no “hacks” in such kind of situations. There is no special routine that can keep you focused just by doing this routine. One thing we can do is constantly remind ourselves what we are doing and why. Every time you gonna start implementing new feature, make requirements and a plan. “I need my users to be able to log into the system. I’m gonna create login form, add empty-field checks and make request to the api”. Follow the plan, make it just work, deliver. Improve if needed. And don’t forget to always remind all of this to yourself, this is the only key - always working to be better. It’s hard, but there is no other way :)

Have a customer to tell you want he wants and then make it happen and give it to him. If he is happy you're done and find someone else to sell it too and if he isn't happy you fix it. Repeat until bill gates pats you on the back. But you better hurry because he is like almost 70 years old now.