Don’t dwell - get over it and move on
One thing that always amazes me in business is the tendency people have to dwell on things and then miss opportunities that are out there.
If you spot an opportunity then weigh up the pros and cons of the opportunity, what it will cost and the expected outcome. If it still looks like a good idea and the costs weigh up then you should do it.
Just as equally, when something goes wrong, review what happened, analyse what you could have done about it and then work out a way forward.
Obviously there are exceptions to the rule but by remaining proactive and reactive to situations you will ensure that you're more likely to survive.
In short, don't over think things.