The better way to tell the difference between sharing and bragging is the timing. If this person always tries to dominate the conversation by relating details of their lives, or suddenly comes up with something in their lives that is better than what someone else just mentioned, it's bragging. When they share a conversation, listening to everyone involved and just adding their life moments when appropriate, it's more likely to be just sharing. Some people don't realize the effect of their life's experiences coming across as 'showing off' when they relate it. Most time, a sharing also comes with offers to take you on their next one, or advice on how to get a great deal, etc. Braggarts just want to prove how much 'better' their lives are, than yours, and it usually means their lives are missing something that has left them insecure. Making up for that lack makes people try to downplay others and demeaning.