When you rarely attend social gatherings like parties, like I do, it is natural for you to feel surprised upon the sudden receipt of an invitation, especially if it comes from someone you knew a long time ago and with whom you have had no contact with for many, many years. On the good side, it's touching to find out that someone remembered you after many, many years of no communication. At least you are not forgotten despite the long gap. On the pressuring side, you will be immediately compelled by the fact that it will be some sort of reunion--and you are wondering how will you compare to that person after all these years.
I think that's already part of reunions. During these gatherings, those who are already confident with their standing in life would attend the reunion, as compared to those who still feel that they have a lot to prove, hence the insecurity. These people would either not attend at all, pretending that they did not receive an invitation, or go to the reunion with insecurity in their hearts, fearing the arrival of the big day. How will you categorize yourself?
During these events, what will you do to impress your old classmates and old buddies? How will yoou show off? How wil you be able to tell them that you are already somebody in your field of specialization? The answer is that you don't have to. No fancy gift wraps and gift wrap tapes will make up to a lousy gift, in the same way that no showing off will compensate for your lack of accomplishments (assuming that you do lack in accomplishments). Similarly, if you have a lot to show off, I guess a little bragging won't hurt, but it would always be best to stay humble and let them know by theirselves of your achievements. Now that would better, wouldn't it?