I am trying to help you with my comment but it is going to be straight. You sound like someone who wants to have the cake and eat it too. If you have the itch so bad, you need to do something about it at some point and there never will be a right time. Trust me on that. Yes, you can take calculated risks etc but overall, there will never be that perfect day.
"Irreparable damage" is too strong of a phrase. That tells me that your itch is not that bad and it is more of a nice thing to do because many others do it. Don't think of it that way. If you truly want to do your own thing, think of it this way. What if you never do it ? Will you be ok with it on your death bed ? If not, do something now. If it doesn't matter that much to you, you are most likely better off just working for someone else.
Having said all this, if you are not sure about how to start your own thing, the next best thing is to join a small company/startup where you learn and are very close to the bottom line. Lot of startups/small companies (under 50 employees) would love to hire failed entrepreneurs.
Source: I have been doing my own thing for almost a decade now after working jobs for a decade. If you are a failed entrepreneur, hit me up. Always open to chatting.