If you are polite and cooperative, the officer absolutely will let you go–but only if you are not and do not appear impaired. According to some estimates, someone dies in the US every 33 minutes due to an alcohol-related crash. When an officer pulls you over and suspects you may be driving under the influence or stops you at a legal checkpoint, their role is not to assess your character but to determine your fitness to drive. In doing so, they are protecting you and others from becoming one of those statistics. If you are driving while impaired, there are no bonus points for being nice about it.
You also have the constitutional right to remain silent and not to incriminate yourself. While you may think it's in your best interest to divulge that you had a glass of wine with dinner four hours ago, this sort of information can be used against you even if you don't feel impaired and have a BAC below the legal limit. If you do not wish to answer a question, you can invoke your right to remain silent by saying so.