Biblically speaking there is something that will kill your prayer life. It will ensure that you are unable to focus, unable to persevere, unable to pray with joy or confidence, and unable to truly delight in the Lord. There is no passage that states that this will kill your prayer life, but there is a passage that says what will enable you to stay alert in your prayer life and by necessary implication its opposite is a prayer life killer. Here is the passage that by necessary implication reveals to us what kills our prayer life: Colossians 4:2 Devote yourselves to prayer, keeping alert in it with an attitude of thanksgiving.
There you have it. If you do not have an attitude of thanksgiving you will be unable to keep alert in prayer. So by necessary implication what kills our prayer life? If an attitude of thanksgiving keeps us alert in prayer, then a complaining grumbling attitude kills prayer. Do you think the Israelites were flourishing in prayer in the wilderness when they were complaining against Moses their leader and their covenant-keeping Lord who was providing for them (Exodus 16)? In Philippians 2:14-16 Paul is clear about the importance of turning away from a complaining spirit: Do all things without grumbling or disputing; 15 so that you will prove yourselves to be blameless and innocent, children of God above reproach in the midst of a crooked and perverse generation, among whom you appear as lights in the world, 16 holding fast the word of life, so that in the day of Christ I will have reason to glory because I did not run in vain nor toil in vain. Turning away from an attitude of grumbling has everything to do with living a blameless life before the Lord.
Based on Colossians 4:2 you could say “Do all things without grumbling or disputing so that you will nurture an attitude of thanksgiving in your heart and thereby keep alert in prayer.” Do you want to grow in your prayer life? Then repent of any spirit of grumbling or complaining that you have been nurturing in your heart and rather ask God to produce in you a heart of genuine thanksgiving unto Him. A thankful heart is a prayerful heart.