I had never mowed grass before a day in my life
Oh yeah? Did you enjoy your first time mowing grass?
It was great. I found it to be very satisfying
I'm glad you found something new you enjoy!  That's always a pleasant feeling.  Good for you!
I think i'll be an enthusiastic mower. I also get to spend more time outside.
I am glad that you're being optimistic about learning something new and I hope you go and find other things that you can do for the first time that you have not done in the past. I am trying to do so as well, and I hope we both have great enjoyment out of it!