I consider practicing fundamental technique to be a hugely important part of being a musician. As a result, I practice my fundamentals as close to daily as I possibly can. For trumpet, that includes "multi-tonguing," or double and triple tonguing. Multi-tonguing is a skill that you need to practice regularly in order to maintain a high level.
I was recently working on my double tonguing and noticed my sound quality deteriorating in the upper register on certain passages. This is not uncommon, and it's one of the reasons I practice that particular exercise. But what was weird was what I did next: nothing.