Obviously with this stickman, its not the subject. Some artists paint portraits without referring to their subject, whether it be a live model or a photograph. Creative? Yes. Spontaneous? Maybe. Smart? Well....not if you care that your painting actually resembles the person you are painting.
Ok, time for a disclaimer: I'm not advocating becoming a slave to the photograph, but if you are painting a person's portrait, there is some expectation that your painting should look like that person. After all, isn't the point of painting someone's portrait to capture a likeness?
One tip that will help is to print your reference photo at a one-to-one ratio with your painting. It makes it easier, because you won't have to transpose the scale of the painting as you move back and forth between the reference photo and your painting. Secondly, keep the parts that you are painting as close as possible to each other while painting. For example if you are working on the right eye of a painting, position the reference photo with the right eye as close as possible to the right eye of the painting. The further away your reference points are, the more effort required.