Giving is just one way of expressing that God has been good to you and will continue to do so through your being good to others.
Humility may well be one of the most difficult of the fruit of the Spirit to be cultivated in us - and to maintain. That's because without humility, it's not likely that you will put your complete trust in God.
We can never make ourselves better by trying... praying more or longer, studying more of the Word, performing good works, etc. Don't get me wrong... it's not bad to do any of these things. In fact, it's good. It's just that doing them in God's power is the only way those things will have any real and lasting effect in our lives.