grits
Explanation
This comic riffs on the experience of discovering that adult life involves tolerating a lot of unpleasant things in order to get to the parts you enjoy — using grits as the metaphor.
In the first panel, a character rants: "I hate grits. They're like nothing. They're objectively pointless. They're only good if you put so much stuff on them — butter, cheese, other stuff — so you pile all this other stuff on top of this terrible base and then you need to tell people that the underlying part is good."
The second panel delivers the punchline: "Boy, you're gonna hate it when you find out what adult life is like." The final panel shows the character exclaiming "Jesus Christ!"
The joke draws a direct analogy between grits and adult life. Grits on their own are bland and unremarkable, but people load them up with toppings and then insist the grits themselves are great. Similarly, adult life is often a bland or unpleasant foundation (work, obligations, routine) that people dress up with enjoyable additions (hobbies, vacations, relationships) and then insist that life itself is wonderful. The comic suggests that the way people defend grits — by burying them under appealing additions — is exactly how people cope with the tedium of adulthood.