How do we know that prayer in Jesus' name is effective?

In John 14:13-14, Christ promises that whatever we ask in His name, He will do it, which serves as a profound assurance of the efficacy of prayer. This promise emphasizes that prayers offered in Jesus' name are not in vain, as they are presented through His mediation. However, this does not mean we can ask for anything; the requests must pertain to our spiritual well-being and glorify God. If we desire to grow in holiness and are diligent in prayer, we can expect the Lord to answer according to His will, reminding us that our struggles are often due to our lack of earnestness in prayer.