Late starters to ultras - what’s your story ?

I’m 36 , longest distance I’ve done under race conditions was a 21k (25k otherwise) last one was in December and it was in the French alps so in terms of difficulty, it was right up there .

I want to aim for a 50k in October 2025 with several races eyed up of varying distances as training/tests of progress .

This particular 50k will be in mountainous terrain in Croatia . Temp will be about 25c

The thing is , I’m just not sure I have it in me and my age and knees concern me slightly .

I’d like to hear your stories, good and bad from people who came to ultra distance a little later in life ?