Why should I give a lecture on this topic?
What is your impact on others? What habits have your friends picked up from you? When you leave a room, what feeling do you leave behind? Or, to use a common Islamic metaphor, what do you smell like?
The Prophet Muhammad ﷺ said, "The example of a good companion (who sits with you) in comparison with a bad one, is like that of the perfume seller and the blacksmith's furnace; from the first you would either buy perfume or enjoy its good smell while the blacksmith's furnace would either burn your body or clothes, or you get a bad unpleasant smell thereof."
Living in the 21st century, it is easy to spend time in environments that are not beneficial. However, we must remember that our time in this world is limited, and it is dangerous to waste it. We cannot let the bad smells of problematic interaction stick to us, and we must not produce bad smells that stick to others.