Once in a while, I learn something about a seemingly unrelated topic - such as freediving - and I take away some trick that is well known and "obvious" in that topic, but is generally useful and NOT known by many people outside. Case in point, you can use equalization techniques from diving to remove pressure in your ears when you descend in a plane or a fast lift.
Reading about a few equalization techniques took me maybe 5 minutes, and I was able to successfully teach myself the "Frenzel Maneuver" by following these instructions:
The technique is to close off the vocal cords, as though you are about to lift a heavy weight. The nostrils are pinched closed and an effort is made to make a 'k' or a 'guh' sound. By doing this you raise the back of the tongue and the 'Adam's Apple' will elevate. This turns the tongue into a piston, pushing air up.
A few years ago, I started regularly doing deep relaxations after yoga. At some point, I learned how to relax my throat in such a way that the air can freely escape from the stomach. Since then, whenever I start hiccuping, I relax my throat and the hiccups stop immediately in all cases. I am now 100% hiccup-free.
I've spent a few hours with a friend who is doing massage, and they taught me some basics. After that, it became natural for me to self-massage my shoulders after I do a lot of sitting work etc. I can't imagine living without this anymore.