The second thing would be not being able to satisfy somebody with your work and they don't want to pay you. I have run into people that are picky about the most trivial things and will hold up thousands of dollars because of it. There is always a solution though, fix the trivial problems and make it right to that person.
My Mama always said " I'd catch more bees with honey than with vinegar!"
A third thing would be the competitiveness in people and careers. Most people don't like changes in any way that has to do with routines and procedures, It's hard to get people to accept a new ways of doing something, even though it might save some time and be easier to do.
Some times you come up against a problem you may know nothing about. Always look to someone who has deal with the problem before and ask them for help. Don't ever be afraid to ask for help!
Good question Denisse!