Prevailing prayer is work, and I'm pretty sure most people are unaware of this reality.
The danger of this ignorance is that many end up measuring the effectiveness of their prayer life by feelings, such as those of beginner's enthusiasm, religious romanticism, or some other sensational ideal of what prayer should be.
Now, feelings are completely unreliable and may or may not reflect the real strength of a person's present faith; but when you don't know that in regards to prayer, you set yourself up for failure. You will either quit private prayer not long after you've begun (because it's no longer exciting) or you eventually respond to a sense of guilt (because it's no longer automatic) by over compensating in some way--and that is a subject too involved for this blog.
The point is, you will often have to approach prayer as an assignment that requires deliberate effort; but when you do, realize that such an outlook does not necessarily represent a lack of love our even purity. It's most likely the contrary.
God is, after all, well pleased with sacrifices as well as long-term intensions--work for His Kingdom! So push aside the feelings basis and look forward to a different, deeper kind of satisfaction. You are called to a life of prayer, a labor of love; and you are called to reap it's harvest.