In theme with busyness.
1. Enjoyment & passion
Days packed with engaging activities feel less busy and stressful.
2. Inner conflict
Time pressure isn’t just about how enjoyable our activities are, but also how well they fit together in our heads. If you have too many competing priorities, you're going to feel busy. If you have continuities, you'll feel less busy.
3. A sense of control
Reactive living makes people feel busy, vs active planning and structuring of one's day. (note: I think this is true, but this can creep towards over-planning your days which will have the opposite effect. Life is too complex to try re-engineering it from a calendar with a handful of goals. I think planning granularity will vary from person to person, but I stick with "keep it simple, stupid" when putting together a Trello Board recently.)
4. Value of one's time
As economists would remind us, when something is scarce, its value goes up—but the opposite is also true. When something is valuable (like time), we perceive it to be scarcer.