Calculus answers two main questions about functions. (1) How steep is a function at a point? (2) What is the area under the graph over some region?
The first question is answered using the derivative and to answer the second question we use the integral.
Nobody is posting their bad days on social media. Social media is not real. You're only seeing the curated part of someone's life. Your life is different from theirs because you get to experience the stuff that never gets posted.