Lucy’s psychiatrists booth is the favorite Peanuts gag of Matt Groening, but he just adores Lucy in general. The concept totally fits in with the mercenary nature of many children, as does the circular logic in much of the advice she dispenses.
What she tells Charlie Brown here, however, is the truest thing Charles Schulz ever put in his comic strip. There is a great curiosity among many people to look at the lives of others not to enhance their perspective on their own life, but to grow envious and resentful and wonder why. Lucy puts it rather plainly (and loudly): Do and die, blockhead. That’s ours.