What may seem excessive to a casual onlooker, like numerous postings of selfies or constant talk about yourself or conversations about your own personal achievements rather than listening to those of others (and tuning out when someone else speaks), is not arrogance. Not egoism. Not lack of manners. If you really stop and look at that person and set your judgements aside, you'll see that whoever is doing it is actually trying to practice self-love. I say "trying" because this is the first stage of it, the first phase of healing. By focusing on self, by sharing self unreservedly, by loving self in any way one can, similar to that of a child who is excited about something, you can come to the next phase, to where you're assured of your own self-love and you can begin having space to love others. Don't confuse this with unhealthy narcissism that comes from the desire to be watched, not to be seen.