I started insanity 2 weeks ago and ive never worked out so hard in my entire life. It was like going from 0 to 10 in a single day. I do it everyday with multiple people that I stay with and im very dedicated but because they keep taking days off because of their aches and pains I do too. the more days I take off the less good I feel. so my advice is to never take a day off unless you have a severe injury. If your muscles hurt I'd keep going,the only way my muscles felt at ease was when I worked and stretched them.
I dont follow the meal plan..I dont have 5 meals. I have 3 meals with a snack between breakfast and lunch. and between lunch and dinner. all mostly 2-3 hours apart. Im too scared to have 5 meals and gaining weight. just do what works for you body