"Then the people rejoiced, for that they offered willingly to the LORD: and David the king also rejoiced with great joy." -1 Chronicles 29:9, KJV.

When we give our tithes and offerings (notice "when," not "if"), we are to do so with a willing heart. God does not want us to give to Him grudgingly or because we have to, but because we love Him. We need to offer willingly. Only then can we truly rejoice in what God has done.