Life is like a restaurant.
When you arrive, the place is already up and running under written regulations and unwritten rules that you may never know and that are unlikely to ever change.
You enter and are probably treated as politely as you treat those who run the place. You are judged to a certain extent on how you dress, but more by how you behave. You are seated, sometimes in a good location, sometimes not, sometimes with luck, rarely with malice.
It appears that you are the first person to ever sit in your particular chair at your particular table. You are not. Many have come before. Many will arrive after. So be polite to those who serve you, for what you request, they will prepare and deliver. How that is done can make the taste of the same dish vary in wide measure.
Be pleasant to those who share your table, for they will largely determine how pleasant your meal is, regardless of what you consume.
Even if you come early and stay late, your time here is brief. You will proceed through the courses and your dishes, finished or not, will be taken away in due time. You cannot get them back once they are gone.
Your dinner companions will, with you, realize that it was an enjoyable time, but you don’t own the table or the place. It is transitory. You will be left with nothing but memories.
Whatever you order, make sure it’s what you want, and what you can afford. You will pay for it in the end.
Oh, and you can leave behind a gratuity of any amount. The people who served you will survive without it, of course, as will the establishment where you have spent time. But if you were given a good table, and dined well, and enjoyed good companionship, it would be in good form to be generous on your way out.