He saved the soul stone for last.
He landed on Vormir and took a moment to appreciate the view and take a look at his surroundings. Steve would have thought the planet was beautiful, with and orange sun and the purple sky, if not for the cold and scary aura he could feel in the air. There was no sign of life at any sight and the gigantic mountain about a mile away from him radiated death.He had tried to delay coming to Vormir as much as he could, but he knew he would eventually have to come. This was were she died. Where she sacrificed herself. Steve had thought when he took the mission that he could use this chance to say goodbye to Nat, but he didn't have the courage to come sooner. How was he suppossed to say goodbye to her? To the one person that had been by his side for almost since he'd been out of the ice? He tried to take comfort in the fact that she'd saved them all, that they'd won, that her sacrifice hadn't been in vain. He repeated those empty words over and over again in his head, hoping that they would eventually ease the crashing pain in his chest every time he thought about her.
She was his family, he would have gladly die for her if he'd been given the chance. But he didn't, and she was dead.
He stood there, staring at the mountain for a while, holding the sould stone firmly in his hand. Then he started walking towards it.
He gave one step. The thought of Nat falling from that cliff made him look away from the mountain and to his feet.
Another step. He realised he would have to see her lifeless body. His vission blurred.
Another step. Images of her laying over a puddle of blood filled his mind. His chest tightened.
Another step. His mind made up the sound of her bones crashing against the hard, cold stone. He could feel his heart poundind painfully in his chest.
Another step. He could see her red hair stained with blood, and her eyes, her beautiful green eyes, just empty.
He stopped. His hands were shaking, he was sweating and he couldn't catch his breath. A panick attack.
He fell to one knee as he tried desperately to get air into his lungs, but it felt like knives were ripping down his throat and his chest was on fire. Even after all this years, Steve had never felt anything like this. It was silly to believe that he was strong enough to take this, it was just too much. He looked at the soul stone as it glowed a bright orange in his palm. That's when he realised he wasn't ready.
"I..I can't" He said, "Not yet"
He tightened his grasp on the stone, and set the coordinates for another time jump. With one last look at the mountain, he left Vormir.
Author's note: Hi! This is the first part of my take on what happened when Steve returned to the past. It was not really established that he married Peggy, so this is sort of a canon compliant fix-it attempt. Also this story is the continuation of my other fic "At the end, it was always you" so if you're interested go read it! I really appreciate comments so don't hesitate to write anything!