Then, it starts to fuck up. Things don't go according to plan. All of our confidence vanishes. All is wrong. We wish we could reverse it. We hope we could redo it. We could rethink the decision made.
Life does not work like math. One screw up decision does not equal one fucked up moment. It is equal to few numbers of fucked up moments. It shall hunt you until you are old and still regretting.
Always second and third guess yourself. Even when you are 110% sure. Make sure you see all the possible outcomes. No matter how arrogant you are, just hear out what others want to say and think about it. Take 20 minutes before you shut your eyes and think about your life.