It's pretty normal to switch between styles of speech depending on the situation. Word and grammar choices you use with a good friend are different than those

It's pretty normal to switch between styles of speech depending on the situation. Word and grammar choices you use with a good friend are different than those you'd use in a television interview are different than those you'd use in court. There are times in your life in which you need to speak with precision, and that means using generally agreed upon grammar and vocabulary. There's no harm in breaking those rules in everyday speech, but you should know them.