Taking a break or cutting back might be a good idea. Maybe lesson 5 is hard for you for a reason. One reason could be that animals are something that you want to draw well and animals are hard to draw well because everyone knows how they are supposed to look. You might be putting pressure on yourself to have a better finished product. That would definitely be discouraging. When we first start learning something it is very exciting and we feel like we are making a lot of progress. Then we move to a plateau and it feels like we are not making progess which is very frustrating. But you are learning, every time you pick up a pencil (oops!, sorry, pen). Eventually you will have another little bump to your learning and you will feel excitement again. Then back to the plateau.

As a person with a full time job and a family, finding time to practice can be difficult. Sometimes my practice takes place sitting on the toilet while my child is asking me questions through the door (All the parents here know what I am talking about). But the phrase that I have put on my wall is "Action BEFORE motivation". I commit myself to doing something very basic, like draw one box or one cylinder, everyday. I usually find that I can't stop there. But if I need to, I can, and I don't feel bad about not doing more, because life takes over and there are important things to do sometimes.