Hebrews 6:9-10 (ESV)
Though we speak in this way, yet in your case, beloved, we feel sure of better things—things that belong to salvation.  For God is not so unjust as to overlook your work and the love that you showed for his sake in serving the saints, as you still do.
God owes us nothing. All that we have from Him is a gift of pure grace. We deserve hell and punishment and condemnation. When we come to Christ it is because He has enabled it, guaranteed it, caused it and accomplished all that makes it possible. The good works we do as believers are the response of grateful hearts for an unsurpassable grace and love. God simply cannot be outgiven.
But all this does not mean that we won’t be rewarded for the good we do after we are saved. If God were to ignore the good works that we willingly and gladly do as His children then He would be unjust. That is what Hebrews 6:10 says. Does the work we do for God deserve a reward from? No, but God has promised to reward us and it would be unjust for Him to break His own word. For the honour of His own Name, for the honour of Christ and for our good. He will not neglect to reward us. God is not unjust. He will not forget the good we do out of love for Him and our bothers and sisters in Christ.
God calls us to service. There are times when we serve and no one takes notice. Sometimes people just do not appreciate the effort, the time, the sacrifice, pain, money that is involved. And even if they did know they wouldn’t care, or at least they do not seem to. To do what we do in order to be seen or appreciated or thanked by others may turn out to be a very disappointing enterprise.
Jesus tells us to do our good works secretly and the Father who sees in secret will reward us (Matthew 6:2-4). What will the reward be? We are not told. But this we know. It will be of far greater worth than the work deserves. That’s just what our God is like.
Do you believe that it does not matter how others respond to your work done for God since God is going to reward you? Do you have such a faith in the justice of God to reward you for your work done for Him that the fact that you are left unheralded now does not bother you? Do you really, really believe that it does not matter who toots your horn or sings your praises? Can you go unnoticed and thankless and not get into a funk of self pity and resentment?
(It is worth pointing out here that if you have to wrestle with how ungrateful and unappreciative people can be then you should go out of your way to be grateful and appreciative. Don’t be what you wish others weren’t.)
God will not overlook the work and love His children show for His sake and the sake of His church. How this ought to make us tireless workers for Him and all His children! Never allow the response of others to discourage you from carrying on in the task of serving God and the church. God will not forget. Set your sights on the prize that is set before you and endure all that life lashes out at you. That is what Jesus did (Hebrews 12:1-2) and you are called to be like Him.
You cannot out give God. Serve Him and His church with great joy and energy. It will be greatly rewarded. It will be rewarded far beyond any reward that someone else might give you. And it will last forever. Keep that perspective and you will be able to serve God just like that.