This pretty much happens to guys that choose to cut off contact with their bros to spend extra time with their girl. Theres a good portion of guys i know who choose to put their girl first almost always. They grow so dependent on their relationship that they lose themselves and arent even their own person anymore. They just become boring.
Its like the relationship is its own person, not too separate individuals. The bros i have who havent turned into this usually spend a considerate portion of time with their bros or by themselves.
Im about to turn 21 soon. And ive never actually been in a serious or ltr. So maybe im wrong and this is common. But i refuse to let myself reach this point.