I think one major element behind beginner's luck is the relaxation that is present before a major difficulty. This becomes especially apparent when interacting with skill with other living things, like animals and even people. One may be tense right off the bat, but usually one is a bit relaxed and playful until one comes up against a difficulty, such as a threat or a failure of one's underdeveloped skills, and becoming conscious of these dangers, one becomes stressed and tenses up, which tends to affect matters of skill negatively.
Skill needs to be carried out in a relaxed and flowing state, instinctually. The more one focuses and stresses, the more the many parameters of successful action are ignored in favor of a narrow set under focus. But in time, focusing on narrow parameters builds skill and these things become automatic and fade into the background, and one once again relaxes.
