It does mean this

Working hard and having something pay off are both very fulfilling in different ways.

Because you work hard, something may pay off which makes you feel good.

But the real happy people are the ones who also gain happiness from the fact that they work hard.

gaining happiness in this way means that you have a certain level of give in your life.

A certain leeway to make your dreams come true as you work hard on something that may pay off in the future, but not in the short term.

Thus, you find the beauty in the long game!