I think the only real way is to find out the reasons behind them, and possibly look at the pros- and cons- of getting married now vs. later. Find a reason that is strong enough for you to want to wait.

I know what it can be like - all of my friends that I went to school with seem to be engaged and about to get married so i know the jealousy, but I also know that my partner and I are not in a position - emotionally or financially to do that right now - and it allows me to move on from the jealousy knowing that everyone is in a different situation and when I finally do get married I will be in a position to feel secure in my own home and without the financial stress a wedding can bring.