God is not selfish. If you read the Bible, God has done a lot of giving and man is mostly only concerned with receiving. But for those who follow Him in faith, this should not be the case. Whenever God blesses His people, He does not intend that blessing to stay in one place, but be beneficial for others as well.
God gave us the ultimate example when He gave freely His only begotten Son to save us. Jesus, on the other hand, freely gave His life for us. It would be a shame if we would not follow their example in sharing with others.
It is not easy to share with others if you do not have enough. But that is God’s problem. If we are willing to share with others, God would continue to pour out His blessings for us, so we can continue to bless others.