Basically all research on who becomes successful show that the one thing that is most important to have to become successful is....GRIT, meaning as Angela Lee Duckworth put it in the TED Talk; looking at life as a marathon not a sprit by having stamina and perseverance. It is actually not about IQ, talent, social intelligence or income, but about whether you keep at it.
Unfortunately there is very little knowledge on how you get this grit, or how you motivate someone to have it and she does acknowledge that as a great issue, one route that her research has shown though is, that when you show a kid pictures of the brain and how it is used during different tasks, and that you can learn and change one little step at a time, their chances of getting grit is higher. That when we believe in change and perseverance and not that IQ or other factors decide our fate we CAN succeed, if we work at it.
From where I sit with my instrument and what playing it has taught me about life, I will dare to say that one way of teaching and motivating kids and adults to have grit, is to teach them how to play an instument - anyone will do. Knowing that practice will make you better at something IS grit. And the cool thing is that it might even be fun and maybe even spead a little joy:-)