Something i started doing which has been invaluable has been getting a therapist. Being a founder is freaking painful at times, working on yourself is a lot more than getting good at sales, taxes, technical skills...developing leadership skills and being great at it requires an upgrade not just to your IQ but your EQ. I've got a long way to go, but i feel this has been the largest improvement to me that i've ever managed to make.
While you're at it, if you do anything along these lines, consider couples counselling too. Even if all is great. The closeness and generally better understanding its given my partner and I has been the greatest stress reducer I've ever found. It opens up my bandwidth to so many other things which more generally allows me to be more effective.