In the early days of anything, most of your energy goes into beginning. Deciding, preparing, overcoming the reluctance, getting the materials out. Once that overhead drops, the same hour contains far more actual work, and progress appears to accelerate even though your effort has not increased at all.

Attack the starting cost directly rather than trying to work harder. Set up in advance, keep the same time each day, remove the decisions. Anything that makes beginning cheaper gives you back the largest share of your energy.