"But this I say, He who sows sparingly shall also reap sparingly; and he who sows bountifully shall also reap bountifully. Let everyone give according to the purposes in his heart; not grudgingly, or of necessity: for God loves a cheerful giver." (That is, cheerful giving.) II Corinthians 9:6-7
If you need Old Testament support, read:
“Give generously to him and do so without a grudging heart; then because of this the Lord your God will bless you in all your work and in everything you put your hand to.” Deut. 15:10
There are a number of interpretations for these two passages. But it would appear that cheerful giving trumps giving out of duty every time.
Next time you feel pressured to give, remember these passages of Scripture. The choice to give is yours. Cheerful giving reaps its own reward.