That line of "reasoning" is flawed in many dimensions. First and foremost, difficulties in life spare no one. You are not alone! And the kicker: one's intelligent, conscious interaction with difficulties is precisely what creates a mature evolved person. In fact, truly successful well-rounded people typically have had a surprisingly challenging life - see Kenneth R. Pelletier's remarkable 1994 book: "Sound Mind, Sound Body: A New Model for Lifelong Health." Simon & Schuster. https://drpelletier.com/
So sticking it out, be it in a marathon or a job, may be the polar opposite of martyrdom and self-abuse - it may well be exactly what you need to grow as a human being. Accepting the inevitability of loosing many battles along the way helps us win the war - and emerge as an evolved wise person.