Might not have occurred prior however, losing energy/focus and motivation from extensive periods of studying is the worst possible thing that can happen and it is extremely common in a lot of students undertaking prelims, even if they "prepared". It is unwise to expend all your energy in the holidays and enter school drained of energy "burned out". Personally, I studied Maths Advanced for 30 mins or so after playing hours on end on the switch and this slowly built up to an hour, then 2-3 hours and eventually a study cycle in which I did not lose motivation/effort in studying. This was in the last 3 weeks mind you, the entire December was spent on games and enjoyment.
Don't stress too much but ensure like everyone said above, that you do put in some effort in the holidays so you are better prepared when you enter school to relieve that stress.