I've been working on increasing my strength and indurance. I will admit, I'm lazy and would rather find something else to do than exercise, even scoop the barn out

They say to do 3 sets of each exercise. How nessicary is that? I do 2 sets, and I'm bored, I don't want to go on. Short attention span?

My goal is to become stronger, I'm not the most physically active woman around. I can cart a 5 gal bucket of water around, and hoist a 50lb bag of feed around and cary/stack fire wood. I guess I'm not the weakest around, but I'd like to be better.

It appears that I've been working each body part 2X a week with some cardio, I'm going to switch cardio up a bit and adding HIIT. The cardio is walking 2-4 miles 4-5 days a week.

Part of me says to kick it in overdrive, stop procrastinating and so the last set, but dang, I don't want to.

So, do I need to do 3 sets? Will I improve faster? Who made up the 3 set rule?