Depends in what situation you are in. For example in my Business Studies class even if I slip up once I will lose my spot and never get it back (since top 10 is seriously competitive, with under 2.5/30 marks difference between 1 and 10 overall).
Questions to ask yourself:
1. Do at least 3 people in your class continually get good marks?
A. Yes (Go to Scenario 1)
B. No (Go to question 2)
2. Were you in the top 5 before you hypothetically screwed up?
A. Yes (Go to question 3)
B. No (Go to Scenario 1)
3. Do you think/is there will be a large gap between rank spots in terms of marks?
A. Yes (Go to Scenario 1)
B. No (Go to Scenario 2)
Scenario 1:
You're fucked! Not really, it just means you probably won't get a good rank (top 5).
Scenario 2:
You still have a chance to make it into top 5.