Before Gravity Falls, adrenaline was the sound of bullies coming up behind them, the knowledge that Dipper's hat would be stolen, his birthmark mocked, Mabel's penchant for the bright and happy derided, harsh words and harsher laughter, the occasional shove or punch or trip.
In Gravity Falls, it was the rush of the chase, the wind blowing through their hair, terror and life threatening danger and glee, the joy of lives saved and victory hard won, fighting for yourself and your family and knowing later, when it all died down, that you'd saved the world.
Once they were home, suddenly, just when they thought things would go back to normal, adrenaline meant the swing of a fist, the defense of each twin of the other, and seeing their bullies back down. It was knowing they'd been through things the other kids couldn't imagine and they'd come out the stronger for it.
Adrenaline was a rush to teenage Stan. A game, protecting Ford, it didn't matter, it was part of the thrill of living and Stan welcomed it.
Then he got kicked out.
And suddenly, adrenaline was danger. It was a gun in his face, a knife at his back, running and knowing there was no where he could find refuge. Then slowly it began to change, as he got older.
Adrenaline was a rush again, or getting away, of making the con, of knowing you made it, one more day you were alive.
Then the kids came. The rush was still there, but the danger was back. Keeping them safe, small arms wrapped around his neck, looking up at him in disbelief or bright glowing smiles, terror at knowing how easy it would be for those two little lives to be hurt.
Small smiles and helpful hands, remembering things slowly yet there were some things that just didn't want to come back, large blank spaces of time that Stan somehow knew he didn't want to come back, but somehow he knew that it was their fault, those missing memories, that adrenaline came with the dusty sweet feeling of a hollow victory some days.
But that was fine. If it was for family, this family that had brought him back when all should have been lost, then it was fine.
Adrenaline was being alive. It was chasing down new species in the 43rd dimension, finding a new fact about a creature in Gravity Falls, and coming out alive.
It was running for his life, hiding in burned out creations that were once buildings, praying to powers that didn't exist in this dimension that he'd make it through another day.
Then Ford was home, and adrenaline was the rush of saving the world, being the hero – until the kids were in danger.
It would take being at sea with his brother for nearly a year before a surge of adrenaline recalled excitement instead of heart pounding terror.
A rush of adrenaline, the sound of laughter, and arm around his shoulder, a million regrets drowned out by gratefulness at this second chance.
And none of them were going to take it for granted ever again.