When you get to this state in a project, you are probably already deeply invested in going ahead, then all the negative voices both internal and external are at their most powerful.
Sit down, take a cup of tea or coffee, take several deep breaths and a pen and paper. draw a line down the paper from top to bottom. On the left wwrite what you think of as positive consequences of you going ahead with the project.
On the right hand side of the paper write down all the negative ideas that you have, if you think you might die include this. Just list as many negatives as you can.
Having drained your mind of the negative possibilities. Take a walk, get some fresh air, maybe another drink of tea or coffee. Stay away for an hour and don't try to come up with solutions for the negatives/ That will come when you get back.
When you have walked a while, go back to your lists. On a second sheet of paper, repeat put a line down the center from top to bottom. On the left, one at a time begin to list the negative items.
As you do use the spacew on the right write down a solution, ask why this negative is so terrible.
If you listed your death, then that is terrible and tragic but even that can be mitigated if one sees this as a completion of a task, life itself, you have no need to worry anymore, you don't have to eat the Brussels Sprouts your mother always boils for three days until they are a grey mush.
Ok you may think that is silly, which it is, but the aim is to come up with as many reasons that you can to negate the negatives.
Be as silly as you need to be, no-one is going to see your lists, they are for your eyes only.
When you look back at this second sheet of lists, you should see that most of the negatives are merely in your own imagination, caused by fear and lack of confidence.
Some negatives will be genuine concerns but the exercise should have given you a list of positive actions that you can take.
Some negatives may even be positive in disguise and you see that in your answers.
All in all in asking yourself What is the Worst That Can Happen? You will have accepted that something may go wrong, and probably will, but you have also created a list of recoveries from those disasters that await you in your endeavours.
As Timothy Ferriss advises in his book the 4 Hour Work Week, "let little disasters happen. Don't try to control every detail, you can't."