I always aimed to be pushing myself to a speed where I was a bit out of breath but could still hold a conversation, as that seemed to be around a heart rate of 130 bpm, so perfect for calorie burning, and as I got fitter made me walk faster and longer to get to the same point!
I am really bad with spiders, the neighbours must have thought OH was trying to kill me in the garage the amount of times I screamed as a spider attacked!