Getting divorced after over 30 years of marriage

Y’all help me understand, why, if you’ve made it through 30 years you can’t hack it long enough to go the next 20? My parents announced their divorce yesterday and it makes me so sad. Growing up I hardly ever saw them argue and even to this day see them be loving and affectionate towards each other. It just makes me think if they can’t make it work any marriage of mine has a shot in hell…

Anyone else experience your parents divorcing when you are an adult? How was it? How did you deal?