You should be celebrating that your nasty sister blocked you on Instagram! Stop trying to win the favor of nasty people. It will only cause you lots of unhappiness and stress. If you hear about milestones in a nasty relative's life, just drop a line or E-card, to be civil, but don't ever expect a response. If you are at a family gathering and run into a nasty person, just say hello in passing, and go hang out with nicer people there, or hang out alone at the event. You are not obligated to keep subjecting yourself to interactions with nasty people. Just let this situation go, and live your own life.
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau