I try to find a musical happy place, something that I know I can play at higher speed cold, with no warm up. I go there, and then I switch back to whatever exercise or guitar solo I was trying to learn. For me that’s the chorus riff from my song “Blood on Our Hands” which switches from 16th note strumming to a few quick 16th note leads that are all picked. I have started doing this to prove to myself that I can play 16th notes at faster tempos and also to remind me of the feel of picking at higher speeds. Maybe for you it’s the opening to “Holy Wars” or “In Between Days” by the Cure. Whatever it is, find it and add it into your practice.