In order to receive we need to believe, which is understood.
But sometimes we may find it difficult to absorb (subconsciously) a belief, which is why we may experience a delay in manifestation.
Say if we want straight hair rather than curly hair. Usually when we want a change, we view one thing as good (IE. straight) and the other thing as bad (IE. curly). If we understand and appreciate both curly and straight hair and perceive neither as good or bad (just variables), we lose resistance to creating full beliefs and therefore manifestations.
It's basically the same thing as accepting yourself!