When we eat matzah, we recline. Then we eat the maror, and we don’t recline. And then we eat matzah and maror sandwiched together, and we recline. Why do we recline? Although there’s matzah, there’s maror there too.
The answer is, when the maror is wrapped with matzah, which is “food of emunah,” he realizes that even the bitter times are for his good. He can now recline for the maror as well. ~ R’ Elimelech Biderman Shlita