I know how you feel, but you know? in spite of everything we have to look for our strength within ourselves. Those who have left is because God has allowed it and He has also allowed us to stay a little longer.
I recommend you not to live in sadness to remember that we do not know when it is our turn to leave so let's enjoy our now as a gift from God and let's look for the happiness of the little and turn it into the much. Let us live grateful for life.