is lower sixth equivalent to S5 in Scotland?
To start off- have you got a study plan/schedule made?? This will prevent you from working too long and therefore, more likely to lead to burning out. Make it clear that it will always be quality over quantity!! It has been researched that a person can only study effectively for 7.5 hours each day, and by the way, that is just an average and so some people may be less.
Comparing yourself to others is okay, but its the way you do it, that's the problem. Use comparison as inspiration- e.g. "I admire what they've achieved, and their success motivates me to keep working hard toward my own goals" To overcome the feeling of 'overwhelm', you should start by breaking up tasks into smaller ones with breaks and rewards in between. For example: today, i need to study a topic that has two sub topics- break them up into two sessions and prioritise the parts where it is really difficult to understand. You can get answers to questions on YouTube and you can get reviews on topics on there too! Use what is already there.
I hope this helps!!