Okay, that happened even before they were friends. They hated each other still horribly and stuff. That's actually why this situation happened also.
It was maybe a week after Pepper broke up with Tony (yeah, she broke up with him). Tony still missed Pepper and nightmares of Afghanistan and Manhattan's alien invasion came back even worse. He was basically having a mental breakdown every night and sometimes even on daytime. But only when Tony was alone. And he told no one about that.
Every day he looked for someone to be with. Just to stop the breakdowns. He was sure that Pepper would help him at night, if he would only tell her that breakdowns started again after she left. But Pepper was still mad at him for ruining one of his press conferences.
Only few days before this story, Fury noticed that something is wrong with Tony. And when Dr. Doom came, he didn't let Tony in battle. Which left Tony alone in the Tower. Gladly, he didn't have any breakdowns then.
But when Fury called Tony to tell him, what happened, it turned everything even worse (if that's even possible). Apparently, absolutely every Avenger was in critical state. Most of them could die any minute. That left Tony alone even for longer time. And the breakdowns were also worse.
One day, Tony gave up. He didn't stand being alone and having mental breakdowns every minute. He missed Pepper, though she was often with him. Nightmares hurt more than ever. Tony was worried about Avengers.
It was already evening. Tony was sitting next to the window, watching how beautiful late night Manhattan was. That's when it hit him.
Memories came in his head, hurting him mentally. Afghanistan, Stane, Vanko, Loki, the dying Avengers. Once it finished, Tony gave up. He walked to the bar and started to drink his problems down.
After 10th glass, Tony took out a gun and put it next to his head. His hand was shaking, he was scared of death. But if it would stop the nightmares, the breakdowns, he could do it. He took a deep breath, his last breath and almost pulled the trigger, before he was pushed against the wall.
Tony was searching for land, but found nothing. He was held up by someone. Beautiful blonde hair, blue eyes that seemed to shine from the tears, scent of apple pie and strawberries. The gun and glass dropped on the floor, as Tony wrapped his arms around Steve's neck. He hid his face in the soldier's shoulder and tears started to form in his eyes.
Steve wrapped his own arms around Tony's back, still holding him up. "Why did you do that?" he asked, voice breaking in the middle of the sentence, as he felt tears running down his cheeks.
"Why did Bruce try that?" he asked back, holding on to Steve tighter. "I felt low. The break up with Pepper, nightmares, you guys… I was having mental breakdowns every time I was alone." He made a pause, not understanding why he even told it to Steve. "I don't want to be alone."
"You're not alone, Tony," Steve muttered and Tony jumped a little because of the 'Tony' not the usual 'Stark'. "You're never alone."
Reason 9: He stopped me from committing a suicide.