I used to grab those cheap hand warmers, then one time my fingers almost froze solid when I was trying to fish. So now I always keep HotHands in my pockets and gloves, it makes a big difference in how comfy I am and how well I can handle.
I use Grabber warmers, they seem to last longer for me especially when tucked into mittens. I like that they stay consistent instead of burning hot at first and then fading when I need them.