It happens and you might never get used to it. It just doesn't seem fair how everything can turn to crap the way it does, but it does and it is a completely natural part of the game. Brett Harris' N0 theorem is a very sobering look at how long you have to play before you can expect to be ahead. It's a year or more for most non-pros.
Had a bad session myself recently. My loser act is a sullen, drunken compulsive gambler, who spews hate (at the cards never others) on losing sessions. The trick is to go with the emotions that naturally arise when losing, God I hate losing! Here's how the exchange went as I left the table down 30 units:
"Color me out, I never want to see this effing place again."
"Sir, please, watch your language!"
(Now this is one thing that legitimately makes me mad in a casino. I don't want to hear a morality lecture from anyone in the gaming industry. It's like getting a lecture on proper treatment of women from a pimp. I don't want to hear it, not from one of them.)
So I decide to give her the business: "What do you mean?"
"You just cursed."
"I did not curse."
"Yes you did, you just swore."
"I did not swear. Just color me out please."
The pit supervisor comes over. "What's going on?"
"He's cursing."
"I did not curse. To curse is to call down a bad thing on yourself or someone else, you know, from God. To say 'May you die and go to Hell'- that's what a curse is."
"SIR!"
"Come on, will you tell her to just do her effing job?"
"She is doing her effing job. Just color him out."
"Thank you, have a great night."
This kind of entertainment takes away a few units worth of the sting of losing!