When do you stop your breath? stopping breath stress you.

when do you stop your breath? and do you notice that?

I noticed i stop my breath below situations.

• when i wait a low website loading on pc.
• when i remember bad memory and fight to them in mind.
• when i think about tomorrow's work and fight to them in mind.
• when im playing game and enemy will win to me.

i thought they makes my heart down. that is only reason.

but i realized "stop the breath" stresses me too.