It's not as much about income itself, as it's about safety. When you know you'll be able to pay your bills in the foreseeable future and you have an emergency

It's not as much about income itself, as it's about safety. When you know you'll be able to pay your bills in the foreseeable future and you have an emergency fund, you can talk how money doesn't bring happiness or motivation. When you're below a safety threshold, barely making ends meet, one car or dental problem from debt, or in debt already, it's a whole different story. Extrinsic motivation will do wonders for you.