The best thing is having an idea about how something works in nature, thinking of an experiment to prove your idea and then getting the data that shows you that your idea was right. But even when the experiment tells you that your idea was wrong it is still useful as it makes you think even harder and come up with a better idea.
In the last year I’ve got to learn to drive power boats, that was pretty fun to be honest! But on a more ordinary, day to day basis, I get a lot out of solving difficult problems that I come across. I also like giving lectures as sharing what I know with other people is really fulfilling.