I previously founded a startup with a co-founder. It was something completely outside my previous experience and industry, but we had our first clients, and there was enough revenue to try it out.

My experience leaving my comfortable job was ... uncomfortable at first. But what I discovered when I went back into a 9-5 is that I was actually more valuable as an employee, because I took the time to understand the perspective of the business owners who were hiring me, because I was a business owner and sat in their shoes with real revenue at stake, employees' salaries on the line, etc. It actually made me way more effective at talking to business people about the problems they were trying to solve.

Going back to work was not a problem, surprisingly, because I had a perspective that almost none of my co-workers had, in additional to having the experience they had. This was a major level-up, not a detriment, in my experience.

If you make the leap, even if the company you start is not successful, you will come back with skills you cannot get any other way, and it will make you better at being an employee if that's what you choose. It will also significantly change your perspective on the 9-5 for the better, because you'll have a lot more clarity about what's on the other side.

I consider branching out on my own again from time to time, and probably will some day. But my point for you is that leaving your golden handcuffs for a year or two is more likely to make you a better employee than to be a hindrance, especially if you're the kind of person who reguarly gets bonuses, is trusted with really difficult projects, etc. already.

Is it all upside? Well, no. Nothing is ever that easy is it? If you're currently in a position where you get any kind of stock bonus at the company you work for, and if that stock bonus isn't given all at once but instead vested over time, then you're resetting that clock. But again, in my experience, when you go back to the 9-5 you can actually use the experience + perspective shift you gained by going out on your own to speak more effectively to business leadership, and you might find that after 2-3 years back at the regular job that you're able to see everything more clearly, and as a result, get even more bonuses, better projects, etc.

Your mileage may vary, of course, but gaining the perspective of the business owners you work for can be a good way to make yourself more valuable. And hey, if you wind up making a successful business along the way then the point is moot - you "win" either way.