While it is true that the plight of humankind is to seek out happiness, those people seeking out a good story want to see characters face obstacles and challenges.
These are the things that bring about meaningful change because they often create a sense of fear, isolation, and loneliness and sometimes rise to the level of life threatening. I would trust that someone has changed after facing cancer more than someone who says they read a good self-help book.
And here is the essence of good storytelling brought to us by the great Mary Karr: No change, no story.
If the characters don't go through significant, meaningful, and authentic challenges (authentic means the reader does not have to suspend all belief) then it is hard for the reader to trust the change the character goes through or to feel it in an emotionally satisfying way.
That said, don't mercilessly or unnecessarily torment characters. This is where the authenticity comes in to play. If the work is fiction, people won't really find it believable. If it is nonfiction, the risk is overstating the obstacle or challenge and/or overstating the change/epiphany.
This issue touches on trust. Trust the reader and the reader will trust you. If you overplay the hand, then that does not bode well.