Impact: "It had an impact on me." So it ... hit you? Physically? Also, "positive" and "negative" re: literature. "This is a positive book." Positively what? I know they generally mean, "uplifting," or whatever, but something can't just have a "positive" message. Positive, when not in scientific usage, has to modify something.

Another: "decimate"! It means to reduce by 10%. If your army decimates another army, you've taken out about 10% of them, not destroyed them or overwhelmed them. If you decimiated your dinner, you only ate 10% of it. I don't know why people think it means destroyed/consumed 100%!