if you tend to be a procrastinator ive come to find the 321 technique rly effective its like when you catch yourself loosing focus you snap back in 3 seconds. another thing is telling yourself to do just 5 mins of study and you end up doing a whole lot more..
try studying in 45,5,45,10 minute intervals or 25 if 45 is too long. Also try to not stress yourself too much for prelims is something I wish I did. Yes its important to establish good discipline and study techniques but dont let yourself burn out over it as again nothing goes towards your ATAR during prelims