Hobbies take a lot of time. You need to sleep, eat, relax, exercise and spend time with family. There is no room in there for a hobby if you are starting a company. If you want to have hobbies it is more realistic to get a job.
Yes, creating a company from scratch is hard. It's a lot of work. Part of that work is taking care of yourself and your cofounders.
If you want to create a successful company, there's no room not to do those things. At best you'll burn out. If somehow your company survives, you probably won't like the culture you created.
To be clear: I'm not saying "don't work hard". I'm saying that if you think you can make it by cutting out all personal time, you don't have the stamina you think you do. Almost nobody does, you're not the exception, and even if you are, you're gambling your company with your own life which, in startup lingo, is what we call a "dumb move".
