A while ago I tried a few breathing techniques which were given in a nice book [0]. I really enjoyed the after-effects of the said techniques so I decided to mix and match some of them etc. The effects were awesome .. at first.
After a couple of weeks, I started feeling very low for no particular reason (no dietary changes or anything) and just downright weird. I eliminated one factor after another and checked if my energy levels were OK. I finally gave up the experiment on breathing techniques and restarted what was in the book. I am good, now.
So.. despite a sample size of one and a trial which wasn't random or controlled (:)) , my advice on this whole thing : Get a qualified teacher and do what is taught. YMMV otherwise.
[0] https://www.amazon.in/gp/product/B07WSBS5S4/ref=kinw_myk_ro_...