"He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty." (Psalm 91:1)
God has really good ears. If you come out with a string of profanity, you gotta know that He wrote down every single "idle word" (Matthew 12:36) and is patiently waiting for an explanation. This is true when you bless as well. In the book of Chronicles it says that "for the eyes of the Lord go to and fro throughout the whole earth…" (2 Chronicles 16:9) And where his eyes go, so do His ears. Phe point is, God hears everything we say.
But then I read in Psalms (66:18) where it says that "if I regard iniquity in my heart, then God will not hear me" and God has my full attention. Of course He hears me. He hears everything I say--inside and out. But until my heart condition is humble and is resonant with His, nothing I pray will get through to Him. There's a difference between "hearing" and "actively listening". That's the implication of the Hebrew word translated "hear" in the King James. And this is what it means when it says God won't hear me. My ceiling is limited by my pride and lack of humility. Think about Paul. God took Him up to the "Third Heaven" and he was so humble he couldn't even refer to himself in the first person when he related the story (see 2 Corinthians 12:2). Interesting.
An "unlimited" or "absolute ceiling" is an aeronautical term meaning you can see forever. Into the blue. If you find your faith is weak or your imagination is suffering from lack of vision, don't despair. A clouded field of vision means you need to humble yourself. Start excavating the sources of God's light in your life. Write them down and dwell on them. And as it says in Psalm 36 (vs. 9) "in Thy light shall we see light". God wants to show us the "wondrous" (Psalm 72:18) vistas that are all around us but He cannot if we choose to cross our arms and pout in self-pity, ignoring the things He's already done.
"And thy heaven that is over thy head shall be brass, and the earth that is under thee shall be iron." (Deuteronomy 28:23) This, because way back in the fifteenth verse of that chapter, we didn't "hearken unto the voice of the Lord thy God, to observe to do all His commandments and His statutes..."
Don't stop praying if you don't feel anything: If you feel your prayers are hitting the ceiling and you find your faith hampered and weak, ask the Holy Spirit for a heart check-up and He'll be sure to let you know if some humility is needed to clear things up. And until you get an answer, keep your face pressed up against the ceiling. God will be sure to remove it.
"But verily God hath heard me; He hath attended to the voice of my prayer. Blessed be God, which hath not turned away my prayer, nor His mercy from me." (Psalm 66:19-20)