During photosynthesis, light energy is used to produce ATP molecules which are then used to construct sugar molecules from carbon dioxide and hydrogen obtained from water. Chloroplasts have two outer membranes and several stacks of small disc-shaped membranes called thylakoids (also spelled thylacoids) inside.
Scheduling a week off will give your body time to do this and will also help you return to your workout stronger and ready to challenge your body once again. Many endurance athletes end their season with a week off and many weightlifters will take a week off from their program every four to eight weeks.
1 If you can't lift it 10 times it is too heavy. (unless you are into power lifting or bodybuilding)  If you are new to weight lifting, you should be sore the day after working out. That should last the first month. If you weren't, you may not have worked hard enough in your strength training.