After 5 to 15 years it's hard, but imagine what it must be like if your spouse leave after 25, 30, 35 years plus?!
I know several couples who had been together a looooong time, like over a quarter century, and one of them walked out. (In most cases I know it was the man,) and the other didn't know where to turn.
In one couple I know, the man left the woman (after 33 years together when they were both 55,) and they had 6 kids (all over 18, all left home.) He moved in with a woman he was having an affair with after only 6 months of having the affair. The wife ended up in a little flat as she couldn't afford the mortgage and bills on her own.
All 6 of the (adult) children blackballed their father for what he did.
Then 2 years later, just as the woman was getting back on her feet, after having a nervous breakdown, and losing her home, her security, her future, her husband, and her happiness; hubby came trotting back with his tail between his legs, as the mistress has dumped him.
The silly mare had him back. Moved him into her flat.
5-6 years on, and 4 of the 6 adult children are still not speaking to their father, and 3 of them won't speak to their mother either, as they are so incensed at what has happened.
Quite a sad story really. The couple (now 63,) don't even know most of their (9) grandchildren, as the is such a massive rift between them and their parents now.