you'll be fine as long as you're consistent. that's the bottom line.. be fucking consistent until you're making good money. no fucking around. work out hard every day, and work hard every day, a solid 6-8 hours. some dickheads around here will tell you to work 12-15 hour days, no, 6 hours of fucking good, solid / quality work is all you need; otherwise you'll get burnt out in the beginning.
the working out bit is to relieve the stress and anxiety you'll naturally receive by being self employed. that's why so many here get fucking panic attacks.. they don't get the stress out any other way.. exercise'll do that for ya.
just my 2c.
There's times you need to put in those hours. Sometimes it lasts a few days other times it can last months. You have to know how to handle it and how to actually take time off to recoup when it's done, but it doesn't always lead to burn out. I've been doing that for around 10 years. I've had 100 hour weeks last a couple months. Does it suck? Yes! However, looking at what you got done in that amount of time and the revenue it's generating is a nice thing.