Like many splitting their efforts between freelance and bootstrapped projects, I struggle to find balance and make sure both are moving forward.
It's not that it's hard for me to find the time for both, it's more that it's hard to find the energy for both. I'm out of brain juice
On your avatar you look young and healthy, you should be able to do more than 4-5 hours.
Managing your energy has a lot more to do with the body than with the mind.
Get your body right: work out, have a good sleep, limit junk food, limit alcohol.
Get your mind right: limit social media, limit reading, watching or listening of anything, even educational during work hours.
Few hacks: Take nap between freelance projects and your personal project, have a workout between the projects, don't eat after 6pm, lower caffeine as much as possible it gives you energy but shortens the daily workspan in my experience.
Very strict timeboxing
Try to reverse your priorities, work on personal project before client work.
Have you read The Power of Full Engagement? If not, I highly recommend it.