I suppose I've talked about routines before here on WIP. Because, you know, they're important and stuff. Everybody knows that. But seriously, they don't. No one knows the meaning of routines - not until they lose them. It's the the most cliched cliche: you only realize the true value of something after you lose it. Now, we could go into the psychology of how missing something you lost is only a symptom of your mind trying to adapt to the new situation, but we're not doing that. Instead, we're discussing a way to correct the situation so your mind, the one that's missing your routines, will have something to cling to while it adapts.
I quit my (nine-to-five-steady-income) job at the end of last year, and with no work that demands to be done - as in if you don't do it, your supervisor will scold you - it would've been too easy to just stay in bed until 4 pm, eating cake and watching Billions on HBO. It could have easily become my new routine now that I no longer needed to work for someone else.
But! Even if you don't work for anyone else, it doesn't mean you don't have a boss to please: yourself, and your sense of self-worth.
Step 1: get the stuff you know you should do, the stuff that will give your life a meaning and that will drive your life forward, first. Don't postpone them to the evening. Do them first and thus tell your mind this is important.
Step 2: if you can, get an office space and work there. Going to that spot will signal your brain you're going to work, preparing it for work mode, and giving your day structure.
Step 3: work roughly the same amount of time every day. You can also use another metrics, such as two cups of coffee or until this subproject is done, however long that takes. This will condition your brain into working a good amount, every day.
...and step 4, remember to have hobbies or do things that you reward yourself with at the end of the day.