Joey may be Friends' hunky hunk, but he's very lonely. He's the only one in the bunch who hasn't found his soulmate, and those aren't the only sad things about him.
Rachel, Ross and the other members of Friends are known for their legendary good humor, but that doesn't mean they have a smooth and hassle-free life. This is the case with Monica for example, some terribly sad things happened to her during her career in Friends . All of them obviously have their problems, but the one that really hurts us the most is Joey. And for good reason, even if the Don Juan of the group is used to short-lived relationships, he feels very lonely. He is the only member of Friends not to have found his soul mate, and it is obviously not the only painful memory he has to face.