I have different routes for my commute and I make a mental note of the times it takes me for each route.

I don't race myself as much as I mildly challenge myself.
I privately celebrate a new personal record, when it happens, but I don't take it too seriously because of stoplights and traffic.

Anyway, staying mindful of my times keeps a little bit of pressure on, and, the different routes keep my body from taking a "set."
I have a long, flat, fast route; a mildly hilly route; a brutal hilly route; and the differences between them give my body a different workout on each ride.

On my non-working days, I have a 12.5 mile route that I ride for aesthetic reasons.
I like the ride and what I see and experience on that ride.
Having a visually pleasant route encourages me.
I note the time and, again, mildly challenge myself.
I have a personal record for this 12.5 mile route of 50 minutes, or 15 mph, which doesn't sound too impressive until one sees the ride: despite its beauty it has some killer hills.

For my seven mile (one way) commute, I typically average 19 mph on the easiest route.
With stoplights working in my favor, and good blood sugar, I have averaged 21 mph.
At 21 mph on my bike, I can match my time for driving the same route in an automobile.

I try to ride every day of the week.

Sometimes I will give myself Sunday off, but only if I have a good ride on Saturday.