Keep playing maps of the same skillset and push yourself. Say you want to improve jacks: you'd play all jack maps for your sessions. If your comfort range is about 100 bpm, play stuff at 110-120. Don't mind it if they're low A ranks, just work on passing them. That'll build the stamina and speed you need to start increasing your comfort range.
(A tip from personal experience is to not play things that you can easily 98+ if you're wanting to improve. Always play stuff you can get an A on, and push yourself until failure.)