As for mental, I got a power meter. I don't look at speed, it's just a nice number at the end of a ride which I like to look at. You'll be happy knowing you're putting your wattage out, and the speed means nothing.
BTW, when i have interval days sometimes I specifically save them for the headwind portion of my route. Otherwise I'd be zipping along at 30mph for a few minutes at a time and I end up covering too much ground. I'll inevitably I'll have a stop sign or crosswalk or something come up.
Looking at my wattage (and kCals burned) for the day in its entirety did make me feel quite a bit better today (I had 36 miles in at a pretty good clip before my return leg). I'll have to start doing that on a regular basis. Unfortunately I'm in law school and just don't have the extra dough to drop on a power meter. YET.