Let me expand on this just a bit --

Like everyone's saying, expect to go slower. If you're not looking at your speed, you won't have that number staring back at you, reminding you of how much slower you're going.

If you can reconfigure your display to NOT show speed, and just show cadence, HR, power, time of day, whatever -- do that. You can still feel good about keeping those numbers up where you need them and not get discouraged by low speed.