Firstly, if you think you are unable to do your essay then you won't, will you? Writing an essay is about, I believe, expressing your thoughts or opinions, connected to facts about which you are writing.
Secondly, if you are going to choose the "best cheap essay writing service," you are doing yourself a disservice. You are a thinking person and should therefore discipline yourself to write your own essay which will give the reader some idea about who you are, your thought pattern, and you may even come up with an original thought. Think about it! You are very likely to enjoy the results of your honest effort, learn from it, and progress.