"If I regard iniquity in my heart, the Lord will not hear me" (Psalm 66:18).
There are many wonderful assurances in Scripture that our God is a prayer-answering God, as well as innumerable testimonies throughout history by multitudes of praying believers that He has answered prayer, often in amazing ways. On the other hand, there are many, many prayers that have not been answered, and the question is: "Why?"
In some cases, of course, it is just that the prayer has not been answered yet, in which case the believer needs merely to continue in prayer, for "men ought always to pray, and not to faint" (Luke 18:1). In some cases, it may be that the request was not in God's perfect will, for, "if we ask any thing according to His will, He heareth us" (I John 5:14). We should always pray as did Christ Himself: "Not my will, but thine, be done" (Luke 22:42), for His will is always best.
There are times, however, when God would desire to answer our prayers, but is hindered by our own actions and attitudes, since He will only act in consistency with His own holy nature and loving wisdom. Some are listed below:
Sin in the heart: "If I regard iniquity in my heart, the Lord will not hear me" (text verse).
Unforgiving attitude: "When ye stand praying, forgive, if ye have ought against any" (Mark 11:25).
Carnal motive: "Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts" (James 4:3).
Selfish family relations: "Likewise, ye husbands, dwell with them according to knowledge, giving honor unto the wife, as unto the weaker vessel, and as being heirs together of the grace of life; that your prayers be not hindered" (I Peter 3:7).
Unbelief: "But let him ask in faith, nothing wavering. . . . For let not that man think that he shall receive any thing of the Lord" (James 1:6-7). HMM