It is accepted that white lies and creating fantasies is sometimes needed to deal with psychological pain specially with children. Sometimes reality is hard to deal with therefore people tend to create complex systems of believes or borrow new existing ones which may have or may have not a scientific basis as for instance religions. The problem with illusions is that sooner or later an unexpected event could wake up from that dream therefore you will suffer again.
Perhaps that process of illusionment/disillusionment can lead you towards more suffering therefore It could be much more appropriate to be realistic about life in the fist place in order to prevent grief and sorrow. Nevertheless not everybody is ready to accept the truth specially when you are emotionally attached to an idea because if you are wrong you would be emotionally devastated.
In some cases truth can help you let of go of pain. E.g. "visiting a therapist and telling lies won't help, however telling the truth to identify the problem can make you evolve personally or even sort it out". Another example could be "visiting a priest to confess your sins". Sometimes not being able to accept the truth about some facts of life or self-deception can lead you towards suffering. e.g. "A model who thought her looks would last forever", "somebody who thought a loved one would never die or never leave"
Are there any remarkable authors and books who believed that truth and being realistic about life could be a better approach in the long run to achieve happiness?
“Sometimes people don't want to hear the truth because they don't want their illusions destroyed.” Friedrich Nietzsche
“There are only two mistakes one can make along the road to truth: not going all the way, and not starting.” Buddha?