Going through this right now. I got rejected for a job last week on a minor detail even though i perfectly met their criteria. A couple things help

• read Ask A Manager, she really helps put things into perspective and has a lot of articles about not having oneitis for a particular job
• Just keep looking. someone will want what you are bringing to the table. sometimes companies make decisions that are completely not rational to someone on the outside but makes sense for them and their team (or is their path of least resistance, like hiring someone's friend...), or they had a lot of good candidates and had to pick on a stupid detail. 90% of the time job rejection really isn't personal and has nothing to do with your skillset or competence but really just someone making an arbitrary decision or a decision based on a fit within a particular team or company dynamic.
• it goes both ways, it really does. my current job that i have had for a long time, i was their second choice and got it because the first choice turned them down. so sometimes you get to be on the receiving end of an arbitrary decision as well.