“Remember your word to your servant, in which you have made me hope.”
God has promised us eternal life in Christ. Clearly He doesn’t forget His own word, so what is meant here? David is bolstering his own faith with this prayer. He is reminding himself that when unbelief prevails and doubt arises, there is a need to stir ourselves to believe what’s true. And, it is a good practice to ask God for things. Even though He is sovereign, and we know He remembers His word to us, it is good for us to humble ourselves and ask for help.