A bit more than a year ago (a long time to be carrying this burden), during a game of football, I made a life-long mistake.
I jumped to catch the ball as it was flying towards me.
Apparantly, during that jump, I shifted too much of my weight  to my left leg and the strain proved to be too great and I heard a tearing sound from my left ankle followed by a bolt of pain. My ankle throbbed with pain as I landed and I limped aside.

I felt my ankle with my hand and discovered a strange bulge which appeared to be the source of the pain. I pushed it backwards and the bulge fell into place.
Later I found out that I stretched one of the ligaments that hold the Achiles tendon in place. From here it could go two ways: either it will heal by itself in a period of 6 weeks up to 6 months, depending on it's severity, or it will never heal naturally. The latter means that operation is nesessary to resolve the injury.

As I already said, it has been more than a year and although the situation has improved slightly and the tendon slips out of place a lot more rarely, the problem is still there. As I will not undergo surgery for a situation that does not have a major impact on my life, this injury is permanent.

It was just a stupid game, I don't even enjoy football, I didn't even want to go.
Now I am stuck with a lifelong injury, just because of one jump. How does something like that happen?

The human body is so fragile.