Whoever told you that love equals fun was lying, or a very great fool. Don't listen to them.

Love is what you do whether it's fun or not. If you love your job, it may or may not be fun. The more important and more life-changing, actually, the less fun you'll be having as you proceed through the learning phases, and the parts where one thing in you dies and gives birth to another, deeper, stronger thing. To create something worthwhile involves a lot of pain on many levels. The more worthwhile, often, the more painful to the point of excruciating. Even something full of pleasure can be simultaneously the death of you, as you pour your soul into a thing that will one day break off and leave you, though you remain in its marrow and its message.
I don't speak of a hobby. This is something much deeper and everlasting.
You love your children, but you wouldn't describe raising them as "fun." More often, words will fail you to describe the experience of watching your heart grow outside your body, and kill you and bring you to life over days, weeks, years.
There is risk, in doing what you love. We've all heard the stories of failure. We have failed ourselves, and only a few rise again to continue as before.
"Going home already?" They watch me untie my apron and clock out.
"Yep. Now I get to start my other job." The scenes with the villain have been consuming me. I'm sleeping sporadically between ideas and images that wake me, exhausted to the point of tears when I come to the end of another long sequence.
"You have another job?"
"The one I do for free." Sometimes I consider freelancing, but bills are steady and the pay is not.
Then there are the days when I think I'd rather starve than go back to the paying job.
"That's not a job, that's writing. It's what you love to do. It's supposed to be fun."
"Yes..."
"Well when you have a job you love, it's not work, right?"
They think of writing as a hobby, like collecting feathers or pinning exotic bugs to velvet-covered cardboard. Odd but amusing.
"No. That's not right." It's not right at all. But that's the great secret among storytellers. We die, doing what we do, and our lives are in the stories.
All you have to do is read them.