Niklas Luhmann said that he never forces himself to do anything; the same is probably to be said about all great scientists, and tool-makers that are "scratching their own itch"
in The Act of Creation Arthur Koestler writes about a monkey playing with a stick for no apparent reason (touching it, pushing things with it, etc.), and then, when a banana is placed outside the cage, suddenly realising ("bisociating") that the stick can be used to get to it - Richard Hamming would probably say that the monkey was forming some kind of Idea Hook
following genuine interest also makes it easier to get very good at something - there's internal motivation, and making even a small step forward feedbacks into the interest, making it easier/more exciting to take the next step, learn more, etc.
this is a useful mechanism for developing an interesting Career, but also seems to work for hobbies and interests in general
this approach requires Being Honest with Yourself - otherwise the interest is not really genuine, and the whole thing might not work that well