A mini-midlife crisis suffered by someone around the vicinity of their birthday.
Symptoms may include paranoia, aggression, grumpiness, obnoxiousness, an inflated sense of self worth, general annoying behavior.
Generally causes by the realization of turning another year older, but can sometimes be brought on by the odd actions of friends attempting to plan a surprise party.
It's the time of year that Matt starts to act like a right fool, talking himself up, acting like he's all that. Wait, it's nearly his birthday - he's having another birthday breakdown!
Sally's friends are acting so weird around her, she's starting to have a birthday breakdown.