I've usually only been in wedding parties of my best friends; around the time when those my age were getting married. Very few of my good-sized family does christenings/baptisms anymore either and I can't remember the last one I went to.

I usually make myself feel better by looking at who was chosen for roles and figure out why that person was chosen; they usually had a longer/better relationship or were more directly affected, a relative where I was just a friend, etc.

Think who you would choose if you were getting married and why, etc. It might reveal what you think about certain people and help you with your relationships with them.