What is “research” supposed to mean in this case? It’s a philosophical proposition, one that has been expounded by thousands of cultures throughout history. If anything, justification for an easy, hedonistic life is the rarity.
My question stands: what does research mean in this case? Are you looking for a scientific study which confirms or denies that “difficulty is more authentic?” It is a question beyond the purview of science. The arguments for such a view would be found in philosophical and religious texts.
Ultimately you end up at philosophy or religion.