Have you tried mixing up games with daily moves with rapid and blitz? Mixing “do it right” with “do it fast” training is more effective than doing only one of both.
I think that blitz reinforces my bad habits of approximate pattern matching and ultimately makes me play worse in my other games. If I want to "do it fast" I can just open my dailies and play them fast! But this is a me problem, I routinely play board games etc too quickly, and lose because of it. I do not need help with "do it fast".