Before doing research on behavior, I never realized how little consciousness humans really have. Mediation is designed to improve consciousness by observing everything as closely as possible.
Consider this. The human brain is designed to filter out information, yet remain responsive to the environment. This is both a coping and survival mechanism. To give some quantification to the filtering mechanism, our senses collect data at a rate of 1TB/s (that's about twice the amount of data your computer can store). The brain can only process a small amount of this information. The information that is processed is sent to different processing centers where sense is made of them. If you are actually paying attention, some of these inputs will be interesting enough to enter your consciousness. You can then think about it.
During a conversation your senses are almost completely saturated. To keep engaged, you need to think and respond quickly. This requires going into your memory, finding appropriate stuff and using it to continue the conversation. You'd think visual and sound inputs are processed at the same rate in parallel, this is indeed not the case. You'd also think that you are perceiving the world in real time, this is also not the case. You are actually living about 0.2 seconds in the past, all the time. To determine what someone is saying and the emotion they are conveying through visual cues requires stitching sound and vision together. Because the processing rates are different, your brain sees a "video" with the audio and video out of sync, like a bad videotape. This contributes to the 0.2 second delay. During this activity your subconscious mind is exposed.
These little spurts of consciousness seems like a continuous stream, but it's more like an 8 mm movie than we'd care to admit. The space between the frames is filled in by automatic responses from your subconscious. These responses are 100% emotional, because subconscious memories are 100% emotion. It is a fallacy that memories are stored more like a hard drive. Memories are stored as emotions and reconstructed to make sense of them when retrieved. This takes more space, but relies upon your conditioning. This is where "having a bad attitude" comes from, it is basically poor conditioning. Unless you actively refresh your conditioning using current conditions, it is likely you will have "inappropriate" behavior.
To complicate the matter further, if you behave inappropriately, your subconscious mind will "protect" you by rewriting what your actions. The clue is when you feel like you've lost time, someone objects to your behavior and you respond, "That's not what I said (or did)". This makes conditioning very important, because it's really all you project and interact with. It is possible to be "100% present". This takes a lot of energy. Most people run out of gas fairly quickly.
Because of this phenomenon, it's very important to practice "clean thoughts". This sounds prudish, and it is. Prudence gets a bad rap. When coupled with stoicism, life can be quite stifling. (I'm watching a series set in the 1950s which is the epitome of a prudent stoic lifestyle that makes any form of emotion seem foreign.) Let's assume it is possible to practice prudence, stoicism, civility and be fun to be around. Such behavior has the effect of creating a personal world that you want instead of attracting what you don't want.