Hobbies are things you LOVE to do. For me it's grooming my horse, reading, riding, cooking, being outdoors doing outdoorsy things, etc.
You can embrace one further and take it along. You said you enjoy writing. So make a little collection of short stories to share with your kids one day. Or poems, or write a novel just because you can.
The best hobbies are ones that you can create and begin projects :)
And it doesn't have to have a thing to do about when you grow up. It can be separate or it can become something more. Up to you
"Strength is the ability to use a muscle without tension"