Now, I work a job were I can easily get 8 hours of sleep a night. Sleep isn't everything but, if you can achieve 8 hours then you are headed in the right direction.
What helps me is taking time to listen to music. Not having in the background while doing other things, just sitting down and listening to your favorite album front to back. Finding times to slow down enough to do these things will help.
Also, I find that yoga is great but, don't get competitive with yourself. Actually just folding into childs pose or something else simple and easy to actively rest your body does wonders.
Lastly, we all work in an industry where there are many options, alot of flexability, alot of understanding of people not performing at 100%. Talk to people. So many of us have been there and yet we stay silent because we only see others' success and hide the struggle.
If you need to, change what you are doing. Change jobs, talk to co-founders, talk to your partner about figuring things out. Burn out can kill you.