The main focus of the story was Steve dealing with PTSD (I think this was how the story defined it, but the symptoms struck me as being very like OCD). Steve's symptoms revolved around a series of numbers which included 1, 2 and 9 (and one other, maybe 4?): he always woke at 2:11am and spent the next x hours running (x is the number I can't remember!); he always had to lock doors twice; his night-time bathroom routine involved doing things (brushing his teeth? washing his hands) 9 times (I think, 9 was involved in some way). There may have been others, but these are the main ones I remember.
One night Tony catches Steve leaving his room at night to go running. Steve is evasive about what he's doing and Tony follows him (I think) but has to quickly give up when Steve completely out paces him. The following night Tony joins Steve again, but this time in the suit.
[Some further details which spoil later aspects of the story.]Tony doesn't know what's up with Steve, but he knows that something is wrong. After the first night, he joins Steve in his Iron Man suit and flies along. Steve totally doesn't want this and tells Tony so, but Tony just ignores him and basically talks at Steve for the entire 4? 5? hrs that Steve runs. This continues on for a while and Tony is sometimes able to distract Steve enough that he can forget the compulsion to run.
At some point, Steve realises that Tony is definitely not getting enough sleep as a result of spending his nights following Steve around. Not sure what happens at this point.
Steve and Tony eventually get together. They talk about Steve's PTSD. Stuff happens?
Steve is very self-conscious about his symptoms. The one bit I remember, from towards the end of the fic, is that they're both getting ready for bed. They may or may not have had sex at this point, but it's the first time they've slept together and Tony has witnessed Steve night time routine. Tony is being amazingly understanding of Steve's compulsion to do things 9 times, and after each time, he tells Steve one things that he likes about Steve. There's an epilogue scene x number of years later, and Tony is still doing this, and he's never repeated himself, nor do any of his 'likes' revolve around Steve's body. Steve is also able to manage his symptoms better, so that they're not controlling his life quite so much. He still has times when he lapses back to the old behaviours, but mostly he can direct the compulsion elsewhere.
The numbers do have a significance - I think they're a year (1942?) - but I can't remember what the significance was.
Found by Spirals: Routine by Wordsplat