Therefore the more we can exercise emotions via various avenues of self-control the more those chemicals will be controlled.
Yes, it works both ways. Since living beings are not chemicals - we are eternal souls “wearing” the body which is made of chemicals, the chemicals are not in charge!
I’ve experimented with “feelings” - it’s possible to create feelings by doing things such as making frightened sounds - you can actually cause fear by doing so, create a sad or bad mood by frowning. Once my children and I started to pretend to laugh - and within minutes we were genuinely laughing, rolling on the floor.
Deep abdominal breathing with inhalation through the nostrils can calm an agitated, angry or fearful mind within minutes. What to speak of alternate nostril Pranayam which is actually very easy.
There are many methods to calm agitation, quell fear, uplift depression using yogic breathing, essential oils, and sensory input of various kinds. Even foods. Many things can help. I treat people with many emotional problems with these methods.