My 13 year old child reached this epiphany just this week (ADHD, not Aspergers). They told me "whenever I think about something, I am really interested in it but then I simply stop thinking about it and do something else." They were a little upset because they wanted to continue with those interesting activities. We had a nice long talk about reaching a maturity point where their active thoughts can control their impulses.

Yes, it is more complex than simply "mind over matter", but it's still an important development milestone.