In training courses, there is an exclusive doubt solving sessions in the end. By the time that session begins, the doubts are all forgotten and this is a scary thing. However, with C1000-153 mock tests, the doubts are solved as and when they arise through the medium of practice. I had a bag full of doubts regarding Configuration and Maintain the Environment topics. However, they eventually cleared and i am much more informed about this part of the syllabus now.