The Laws of Prayer (The morning services) (34)

1. A person should pray slowly and in a manner of supplication, like a poor person who requests help at the door. (Shulchan Aruch and Mishne Berurah 98)

2. A person should be very careful that prayer does not seem like a burden. and that it does not look like he is only praying in order to fulfil his obligation to pray. Instead, he should pray in the manner of someone who needs something and is requesting it from the king who has the power to grant his request. (ibid)