It's like pushing a boulder up a hill, only to have the hill just be a never-ending staircase of derivatives and integrals.
Why is calculus hard? Ask the ancient Greeks, who were like, "Hey, let's just make math harder than it has to be, and watch as the Romans run for the hills!"
Why is it hard? (A tale of two variables)
Solve for X: A calculus puzzle
Limits: The point where math goes to die
Differentiate with me! (A calculus sing-along)
Or, you know, just give up and eat a sandwich.
Calculus is hard, folks!