I think that the important thing to remember when approaching these types of questions is that the interviewers are trying to look at how you respond to certain situations.
Admitting to being stressed, or perhaps making a mistake, or discussing a weakness of any form is an opportunity to discuss and portray the following:
- self awareness
- critical self-analysis
- your ability to learn
- your ability to adapt.
This means that the best answer to a 'weakness' question is perhaps not "XYZ was difficult but because I am a superhero I managed to slay the dragon AND avoid the shark infested custard."
It is something more akin to "I struggled with this aspect, it taught me this, I went away and worked on that weakness by doing XYZ, and now have a better understanding/more positive results."