Grace having to turn off the gravity for some reason on the Hail Mary, and the second Simon goes weightless he immediately curls into a ball and braces for impact.
Memories of being thrown around like a ragdoll, banging against the walls, heat burning through his clothes and blood seeping into his skin. That feeling of being dropped into the blood ocean the second time and subconsciously knowing he'd never come back up. Weightlessness being a fun form of movement for Grace, but a reminder of losing control for Simon.
But Grace is there now. He gently calms Simon down, reminds him over and over that this weightlessness is under their control. He helps strap Simon into one of the chairs in the cockpit and demonstrates the slow come down, the careful stabilization of the centrifugal system instead of the violent slamming of the SM-13.
The next time they have to turn off the gravity, Grace offers Simon to stay in the chair this time, but he declines. Simon's the one to pull the switch, to make the choice for zero gravity. He learns to move around using Grace's weird webbing system, actually has a little fun with everything floating around. Grace and Rocky have a spinning contest and they only learn Eridians don't have a central balance system once Grace nearly throws up and loses. Rocky's < Victory victory victory, Rocky always win with Grace !!! > gets Simon to truly laugh.
Simon clings to Grace once it comes time to turn the gravity back on. Rocky was okay with flipping the switch, and Simon didn't want the chair again. Grace has him at arm's length by the shoulders, Simon's one hand holding tightly onto him.
Simon can feel the change this time. The slow pull to their relative floor is relayed to him every step of the way. The floor is cool when his feet naturally reconnect with it, and the weight of his own body is gentle on his legs as he rests. Things fall carefully, nothing breaks, and Grace never lets go.
Simon's not entirely used to his own legs just yet, when he tries to take a step forward and fumbles. But Grace is still there, catching him, chuckling at his own memory of the same thing happening to him the first time.
And when Simon looks up, sees Grace looking away at his own embarrassment but still smiling so bright, he feels grounded for once. Yes, he will need to drift sometimes. But at least this time, he'll have one soft landing waiting for him.