You are going to screw up, something is going to go wrong, what you are trying to accomplish will not work.
You will fail.
But worse than your failure, will be your inability to see that you have failed, to take the opportunity to learn from it and make yourself better next time.
Celebrating failure is great, it signifies effort, endurance and commitment to keep trying.
Not learning from failure ensures that you will inevitably fail once again, in the same fashion, over and over again.
Take the time to do more than celebrate your failure, take the time to notice what went wrong and what you need to do next time to make it a success.