It came up again today in yoga class (cops this aft) about how yoga is supposed to be relaxing. This also came up on Sunday during the meditation workshop. Especially with meditation, it is like a mirror - you can see yourself - so if you're not relaxed and you show up to meditate, chances are you may notice you're not relaxed. And meditating won't necessarily relax you.
Same thing with yoga. It doesn't necessarily relax you. Sometimes yoga is quick. Some of the breathing is really fast. And sometimes it's slow. Sometimes people slow down and it's not relaxing to be slowed down. So context is everything. Depending on when you're doing your practice, depending on who's doing it, what's going on, where it is, what you're trying to accomplish, and many other factors, it may or may not be relaxing.
There's no guarantee that people will be relaxed doing anything. And different people get relaxed by different things. Somethings that relax one person agitate another, or agitate the same person at a different time. Getting it right is an art.