Enjoyment. There are so many ways of enjoying what you're doing and they vary from person to person. For example, there are a lot of people who ride their bikes and take hundreds of pictures of where they've been and what they have seen while riding, yet I like to get lost in my rides, take the time to fully take in what I experience and be left with the memory, that is all my own.
I've been a professional Cyclist for 9 years now, and most of the people I meet in "regular" jobs always tell me that they are jealous of my job and it must be perfect. The truth is, there are plenty of times in the last 9 years where I have hated cycling, but I am still here today. It's a cliché to say, but nothing worth having comes for free. I've always managed to keep a strong idea in my head of why I chose the path I was on, so when I am finding things difficult, I always go back to that reason I started cycling - to get lost, explore and experience the world just to myself.
What I'm eluding to is that there are going to be times when you're not going to be happy, but that's OK, those hard times make it possible to enjoy things long term as long as you always remember the reason you started! So if you enjoy riding hills as hard as you can or just enjoy a nice slow group ride with a cafe stop, the beauty of cycling is that those things are always available to you.