...actually, that's not a thing you do in Zen.
Pedantic musings aside, I like Zen meditation a lot. I enjoy and will participate in many forms of meditation, but for my own practice, I like going with "simple" Zen. No mantras, no visualizations, just sitting and breathing.
If you're not used to doing Zen meditation, it can be horribly boring.
I was pretty diligent about doing twenty minutes of Zazen (ie, sitting meditation) a day for a while several years ago, but I fell off the wagon and my attempts to get back on it were half-hearted at best until recently. At time of writing, I've worked myself back up to twenty minutes a day with the hope of getting to a full half-hour in the next couple of weeks.
I am definitely not an authority on how to do Zen meditation, for that there is no substitute better than a honed practitioner who knows how to teach (granted, I haven't done Zen in a group setting or with a teacher for quite a few years so...). There is a lot of writing out there on Zen practice, but ultimately you have to sit on your ass and just DO THE DANG THING. Zen is best learned by the doing of it.
The reason I started getting back into Zen is simple - my brain's been too chatty recently and it's making me unnecessarily anxious. That's the main thing I've learned about myself while doing Zazen: I have too many thoughts and I am much more calm when I can get myself to let them go. Like doves from a magician's hat. Be free.
Zen isn't about being unflappable or at total peace per se, it's about seeing what's happening, acknowledging it, and acting accordingly without getting too tangled up in your pesky thoughts.
Oh yeah, a more seasoned practitioner is definitely cringing right about now.
Everything is impermanent; people, pets, objects, nations, and especially, thoughts. Wrestling with this is one of the key points of Zen.
Zen is, as far as meditations go, quite difficult sometimes (for me especially, given my talkative brain). It's a mindfulness meditation where you can focus on the breath, but ultimately, when one feels comfortable doing so, you let go of even that little mental handhold. The mind is prone to wandering and bringing it back to a neutral state over and over again is just... what you do when meditating.
I'm sure I've completely butchered what Zen is, but I wanted to talk about it because I've been finding it supremely helpful and centering. There are so many deeper levels to Zen mediation that I'm only barely scratching the surface of and have zero authority to speak to. If you want to learn more, the books Opening the Hand of Thought by Kōshō Uchiyama and Zen Meditation in Plain English by John Daishin Buksbazen are my favorites, but again, having a teacher really really is essential.
If you've been doing Zen for longer than I have, I'd love to hear from you. If you haven't and just want to shout at me, that's cool too I guess.