How is your diet? Sometimes I notice that if I'm not eating properly my mind plays tricks on me and I feel like my workout is harder because I know I need to burn extra calories I consumed. Also give your body time to adjust. It's supposed to be hard. I remember being on week 3 and 4 and having to repeat because I wasn't prepared to move on. There's nothing wrong with that. I think the best advice I've heard is no matter how slow you go, you are still going faster than those still sitting on the couch