A lot of guys do pussy/stupid shit when they're whipped on their first ever girlfriend. This is the excuse they can use when their buddies rag on them for it.

when a guy loses all contact with his friends to spend time with his first girlfriend, which will inevitably end with him dumped and without friends

First girlfriend confidence boost or FGCB is a condition that occurs when someone who is socially awkward and has no history with women finally gets a girlfriend. They person will begin to think they are cool, even if there girlfriend is unattractive and they will think they are "the man" because their penis gets touched for the first time, failing to realize that everyone's has by now. They may try to act like a tough guy because they are taller than their girlfriend when in reality she is most likely just really short. The only cure for FGCB is a breakup which will destroy this newly found ego.