The Bard said everything best, of course, and he's making my point here but he's making it hyperbolically: "'Tis nothing good or bad But thinking makes it so."
O Bardo contouno todo mellor, claro, e defende aquí a miña versión pero faino de xeito hiperbólico: "Non hai nada bo ou ruín/ Mais pensalo faino bo ou ruín".