Trying to change an unhappy person will make you VERY unhappy. Just be your happy self. They’ll choose Happy when they’re ready.
If you hire an unhappy person, there’s little you can do that’s going to change them. Hire happy people.
Unhappy people find a way to be unhappy until they’ve had enough of it. Sadly, some want more than enough. Enough of that.
Having all the right skills on paper will not make an unhappy person a great performer.