If you too stress you can always choose CCA like being an
librarian or music like choir if you have the knowledge, that how
most of people I know 'de-stressed' themselves when the CCA 's
rules change their activities day on weekday instead of weekend.
And they know that O/N level are the most important step which they
cannot failed.
If you are scared of using CCA to apply in poly, I can clearly
tell you that they will only look at your O level or Nitec grade,
your CCA is just only an bonus cos I know of people who are O level
private candidate can still being accept into their course.
Finally for employment wise, most employer did not even bother
to see like your NS certificate of service to see how 'good' you
are, let alone your CCA which only reflect on your report book.