Have you ever been around someone who received some really good news and you couldn't help but to celebrate as though it were your own personal victory? I sure have. In fact this happened to me yesterday.
In 1 Thessalonians 5:12 NIV the Bible tells us that we should be joyful always. If we're supposed to be joyful all the time then rejoicing when someone else receives a gift from God shouldn't be a foreign policy to us. Being happy for someone else and making that happiness known only makes the good deposit (2 Timothy 1:14 NIV) entrusted to us mature, which is the very reason that God gave it to us in the first place (James 1:4 NIV).
When someone else receives a blessing be like Elizabeth's baby and leap (Luke 1:41 NIV) with excitement.