“To be capable of steady friendship or lasting love, are the two greatest proofs, not only of goodness of heart, but of strength of mind.”
~ William Hazlitt (1778-1830) English Essayist
To prove you are a good friend, you need to show the goodness and character of your true heart. If you don’t or can’t do this, then you are more or less wasting your time with someone if what you seek is a sincere long-term friendship. Nothing lasts forever, so you might as well make the most of your friendships since life is short.