Don’t be late. Always be early or punctual. Being on time for appointments is a basic form of respect for others and for others’ time. It shows you regard the others as important people in your life - important enough for you to properly plan your time.
The most common reason I hear to justify lateness is this: since others will be late, I should not waste my time to be early or punctual, and then wait for others to arrive. Instead, I should be late as well. A tit for a tat.
First and foremost, two wrongs don’t make a right. Just because others are late, does not give us a free pass to be late; just because others disrespect our time, does not give us a free pass to disrespect theirs. Our principles for punctuality and respect hold true always - regardless of others’ lateness and disrespect.
Often accompanied with this tit-for-tat reason for lateness, are frustration, irritation, possibly even anger. Remind yourself on the separation between what is controllable and what is not. The actions of others are not within our control. And so, as much as possible, we should not let something not within our control to affect our emotions.
Tit-for-tat is also the worst scenario in the Prisoner’s Dilemma - a lose-lose for everyone. We can instead choose to bring everyone out of a lose-lose situation, by first being punctual consistently - an action that is definitely within our control. By showing everyone that we are willing to be punctual consistently, we are offering a gesture of goodwill. Again, whether others will return the gesture is beyond our control. But, at the very least, we know that we have tried our best.
Finally, if we have no choice but to be late, because of a traffic jam, a train breakdown, or a last minute meeting by your boss or customer, then we should have the courtesy to inform others as early as possible, and give an estimation of when we can arrive. This is again a basic form of respect, and especially practicable with the help of smartphones today. The traffic jam is not within our control, but a short WhatsApp message is, surely, within our control.