He belonged to the rebellion and these were the effects of his adrenaline - just flying and driving his X-Wing, let alone destroying nearby TIE fighters, really gave him a lot of stress. Especially where he was supposed to go on a mission, with you in the same ship, to destroy the Death Star. He just had to successfully launch his X-wing fighter's torpedoes into the vent, impacting the core and triggering a catastrophic explosion, along with your help to cover him. It seemed simple.