As a founder do you take one or two days off a week?

If you look for a good work/life balance, I think it's more important to have strict rules during the single day, like "don't work after dinner" or "do sport just after wake up".

What does “as a founder” have to do with it? New species of human?

Founder or just regular person, we all need time off from work. How much and when will vary by person and the requirements of the job.

As the “founder” of a solo freelance business I try to take weekends off but sometimes I have to get some work done.

Like, in addition to weekends?