Don't you mean, "Don't be afraid to make mistaeks"?
I may not be qualified to give advice since I'm working on my first ground-up game myself (though I've been modding for decades), but I started with a sense of vision -- how I wanted the gameplay to feel. And that invariably has to cross paths with the flow of combat. I think this is where tire meets asphalt and a lot of game concepts go to die. Dice rolls, flavor text -- that's all fine and good until the first time the players try to fire ranged weapons from a runaway wagon and everyone spends the next twenty minutes poring over the rulebook to try to figure out how it's simulated.
I'm not sure this was mentioned but I'm going to jump into it either way and I know, before I even give the advise, that it is very tough to follow.
Leave emotions behind. I don't mean leave your excitement about creating your game aside because that is almost a must, that passion is a key to finishing your game.
What I mean, is the personal level. When you present it and honest players are like "Ummm...I don't really get the point of X" then don't take it personally. But even more important than not being afraid to fail in creating your game, don't be afraid to fail those working with you either. Just like war (without the threats to life), they know what they are getting into and clearly that a game can either succeed or fail. Don't let your collaborators pressure you, especially if you are truly going to be the owner and the "boss" of your project.
Focus and forge ahead. As someone whose head has way too many worlds, hobbies, and creative interests, I know very well how easily it is to be distracted from any particular project. I'm still deciding whether to finish a RPG or a novel first, myself. It is not a good place to be in.
A lot of aspiring fiction writers have a similar anxiety and the best advice I've heard is: "Fake it until you make it." Every game designer began somewhere, and this hobby was built on people just like you.
As far as your actual game goes: build, playtest, evaluate, repeat. Actively try to break the system.
If the whole thing is too much, focus on smaller portions or sub-systems, maybe focusing on the essentials first. Steve Jackson's first RPG was marketed as a simple gladiatorial combat game (Melee), to which he then added magic (Wizard), and finally a skills system (In The Labyrinth.)
Don't worry about art, yet, because you can use whatever graphics you can beg, borrow or steal until you're ready to market the thing.
Find game conventions and store events that cater to demo'ing new games. If necessary, re-skin your game to fit an existing property (movie, book, game, etc.) to give players a familiar frame of reference (until, of course, you're ready to sell it.)
Focus on players and creating a fun experience for them. Limit explanation of game mechanics and background and let players get into the action as quickly as possible.
I haven't read the whole thread yet, but this is a generous community and hobby so you will no doubt get a lot of help and advice.
My one thought just now is that you can always release your game in stages or editions or iterations: quickstarts, walk-throughs, actual play videos, basic sets, deluxe sets, revise editions, etc.
Don't be afraid of putting out an "imperfect" product - you can always make an updated version. It should be solid and competent from the get-go, of course - don't be shoddy. But don't let "perfect" be the enemy of "done". Get it out there.
Your first replier had the best and most sobering advice I have seen and every word gospel truth, I am friends with people that run game companies. The main reason I noped out of the whole process decades ago. I want to play and enjoy games, not work on other people playing and enjoying games.
It is a hard and unforgiving industry. Much the same can be said of any creative industry. The dues are heavy. The rewards thin and fleeting. I know of no one that has gotten rich on it.
Decide, do you want to play games or work games? If you have any chance at success you will not do both.
It's best to try getting past that block ASAP. I'm in the process as well and the first most valuable experience I had was posting to r/rpg and just hearing what people had to say. The whole process is extremely difficult but interacting with people who know and love the hobby is a huge boon. It sucks at first, everyone is going to pick everything apart. But you have to come back and do it again and again.
The moment when you start getting more compliments than criticisms is amazing.