• Not sure whether a JC or poly would suit me (I think I'll suit better in a JC because I'm more academically inclined, but part of the reason why I prefer a JC may be because of an underlying assumption that JCs are better than polys)
• Not sure whether I can cope with the academic requirements/stress of going to JC
• Getting grades that aren't ideal so I can't go to my ideal JC/poly course, so I have to search for other options in the 5 days I am given to choose which institute I have to go to
• Unknown/unexpected challenges that will cause me to be unable to focus on studies (parents divorcing? friendship problems?)
• Choosing subject combinations in JC 
• Getting tired easily so I can't study as much as I want
• Lack of organization skills which will take a toll on my performance
• Failing to make it into a local university with A level grades, so I'll have to start again with a course in a poly
• Choosing a course in poly/subject in JC which I would come to hate
• Interacting with people in general
• Lack of study spaces?

These are reasons why I am also anxious and excited to get my O level results back, so I can have these questions answered once I get my results/resume schooling. Maybe I will find myself in a position completely different from what I have thought, but at least I'll have some answers.