A long time ago in a far away land (New England) my family spent our summers on a lake in NH. Since I was constantly around water, boats were my life. When I finally got old enough to start working and saving a bit of money I bought a radio (MRC) and a boat kit (Dumas SKdaddle JR). I built the boat, installed the engine and radio and had a ball. I also used the radio in a car. As I got a bit older I found a group who raced boats. When I hooked up with them I built a more serious boat and raced some. However, I had also seen a guy who used to fly his float plane on that lake in NH. Eventually, I found a hobby shop that specialized in planes. With the help of the hobby shop owner and one of his friends I built a plane and learned to fly. This was a couple years before I graduated from college.
On graduating from college I moved to NC. I arrived here on a Friday afternoon and went flying on Sunday (I would have gone flying on Saturday, but discovered there were full scale boat races in town
) . A couple years later I found a group who raced boats, so I got back into that. I also branched out into racing cars for a while. I still fly (obviously), and recently got back into boat racing. I really like boat racing, but it's only fun if you've got a good group to race with. I only run my boats at a race, or when getting ready for a race. I enjoy the challenge of racing, but wouldn't have boats if all I did with them was run them in random patterns around a pond. Cars were the same, only interesting in a race environment.
For me, flying is both relaxing and challenging. I can take a couple planes to the field and just bore holes in the sky, shoot touch and goes, etc, relaxing. Yes, shooting touch and goes is relaxing for me.
Or I can challenge myself with aerobatics, low passes, flying inverted, formation flying with a buddy, etc. When I'm in the mood for a speed fix I bring my Shrike to the field.
Out of all of the possible R/C branches I think flying presents the greatest personal mental challenge. Boat and cars are more about setup, competition, and lots of $.