John 9:4 – “His sheep follow Him because they know His voice.” (NIV 1978)
My Musing – There are two reasons why people might not know the His voice. First, they might not know Him, they are not saved. Second, while saved, they have not developed a close enough relationship with Him that His voice is recognizable.
My Advice – If you find it hard to know whether or not God is “speaking” to you, then you probably need to work on the relationship. Are you getting sufficient exposure to His Word by attending church regularly and daily reading/meditation, that when He speaks (through others, “feelings” circumstances, etc…) you know it is His “voice”?