Hierarchically decompose your total distance and count it out at each order of magnitude. I used to row indoors quite a bit and would count each 100 meters, incrementing to track each 1000 meters. Helps both to focus on short term goals but also feel the progress toward the longer term goals.
That said, my fitness incremented by orders of magnitude by getting outdoors and when confined to indoors finding a way to play video games at the same time. This week, I've done 3 rides greater than 50 miles for what it's worth.
Nintendo Switch controller. One half per hand is ideal for cycling, IMO. I wound up getting an adapter to play PS4 games with a Switch controller (also PC emulators). But there are a bunch of good turn-based strategy games for Switch which work really well.
That said, my fitness incremented by orders of magnitude by getting outdoors and when confined to indoors finding a way to play video games at the same time. This week, I've done 3 rides greater than 50 miles for what it's worth.