Discovering a leak (waders or pontoon)
On unfamiliar waters, recognizing the take out
As for being killed by a mother bear in YNP on a cold October day, what a way to be remembered! I always tell my kids if I die remember I was doing what I loved. I just hope she (the bear) has the courtesy to kill me after I've fished for the day.
Up until I'm actually fishing: I'm worry that I forgot something important (rod, reel, boots, license, flies..).
Once I find I have all I need and I'm actually fishing, the only thing I worry about is theft/vandalism of the car.. it really ticks me off that I have to worry about anything while I'm fishing, so I doubly despise thieves.