During the chapter Kamala, Kamala asks Siddhartha what skills he knows. He answers: "I can think, I can wait, I can fast." (page 46). He mentions afterwards that he can write poetry, but this feels secondary compared to the first statement. These skills, although they are apparently lame, are what made Siddhartha successful. He waited for Kamala to love him and help him; he fasted so that Kamala would give him delicious food, and he thought before he did any of this, making sure his plan would work. These skills were not only useful with Kamala, but also, later on, with the merchant as well. In The Karate Kid (1984) is about a kid who is taught karate by a handyman. Mr. Miyagi, the handyman, teaches karate in a different style, so Daniel believes that the skills he is being taught are not karate related and, thus, useless. Yet, lame, as they might be, they made Daniel the karate champion.
Anyways, in both works some apparently useless skills become useful, and both have a happy ending (at least for now in Siddhartha). So, although thinking, waiting, fasting, waxing, sanding, and painting may apparently not be connected to karate or usefulness, don't underestimate the power of the Buddha. (Or the handyman/sensei from Okinawa).