The Apostle James wrote: “You ask and do not receive, because you ask wrongly, to spend it on your passions.” (James 4:3 ESV) In other words, selfishness is a major hindrance to effective prayers. When your prayers are seemingly centred upon what you think you want, you deviate outside the true purpose of prayers. For a prayer to be truly spiritual, it has to go glove in hand with purity of soul, and no matter how noble your intentions might seem, selfishness will eventually lead you to sin. Prayer is not to be simplified into meaning a way to get what we want. God is not some wish-granting Genie.
When prayers are offered from an exclusively personal perspective, such prayers are selfish. When we do things (anything at all) without any consideration for God or other members of our community, we are clearly in the wrong. Selfishness corrupts. Selfishness will eventually lead to full-blown lust and greed fuelled by hedonistic pleasures. When you pray from a lust-filled heart, you commune with yourself and such activities will steer you towards exalting yourself above everything and anyone else, including God. This was not your original motivation, but overtime, you might no longer recognize the difference. These things can be subtle, but the sincere person is able to discern.
So, prayers should be offered from a pure heart untainted by lust, greed or ambitions. It should be offered in faith and moulded by love, selflessness and taking responsibility for others. You have to ensure you are actually reflecting the mind of God in your prayers. And you do that by knowing the will of God. Jesus famously lambasted the religious leaders in his days, “You are wrong, because you know neither the Scriptures nor the power of God.” (Matthew 22:29 ESV)
The will of God can be understood by reading the Bible. When you read, you get better perspectives on issues and will be able to pray in a manner worthy of a true watchman.