A person should not eat nor drink before praying Shacharis. It is considered conceited to do this because a person is taking care of his physical body before his spiritual soul. A person may drink water, coffee, or tea before davening because this is not considered conceited.
(NOTE: people that NEED to eat before davening should talk with their Rav about the specifics on what they should do. There are numerous options.)
4. Be kind to yourself. Speaking badly even about yourself is unethical.
הלכות שמירת הלשון 