The most common post YC failure case for the companies we fund, is they're incredibly focussed during YC on their company... and after they start doing a lot of other things. They advise companies, they go to conferences, whatever.

... you want to be proud of how much you can get done with a small numbers of employees.

The thing that kills startups at some level, is the founders giving up.

Someday, you need to build a business that's difficult to replicate. This is an important part of a good idea.

The startups that do well are the ones that are working all the time.

If you look at successful pivots, they almost always are a pivot into something that the founder wanted. Not a random made up idea.

Unfortunately the trick to great execution is to say no a lot.