Back in my distance running days, we always classified our runs into one of two general categories -- "long, slow base" runs, and "performance/training" runs.

The performance runs always had some route and component to the run where we pushed things, working on certain aspects of our running abilities. Harder hill climbs, intervals, sprints, whatever.

But it was the long, slow, "running base" efforts that always grabbed me and kept me coming back. I could de-emphasizing the specific performance aspects needing work, but instead focusing on better connecting mind/body/spirit on the run. Managing the breathing, going at a pace that could be sustained almost indefinitely, "recharging the batteries", taking in the sights along the way. Turns out, these sorts of runs developed into much more rapid pace, as we improved our overall conditioning and performance. But it was also on some of this moderately-quick "base" runs where I would most often get that almost-euphoric "runner's high" feeling.

Learned to apply much of that to my cycling. Mostly, I have always done A-to-B transportation cycling. The "long, slow base" type approach seemed to have worked well for most of my rides as well. These days, I've got old injuries that preclude any sort of performance running or cycling, but longer, moderately-paced or slower-paced rides still appeal to me. It's what all my rides consist of these days. No "cycling high" feeling from the exercise itself, in terms of the endorphins, as I no longer push that hard. At a certain pace, it's almost meditative. But from a "battery recharge" standpoint and better-connecting with the experience ... it still works. And I still love it.