Your question reminds me of Star Wars... Was it Vader or Palpatine that urges Luke to use his anger? Join the Dark Side?
I'm not sure anger is necessary in the situations you mentioned, and this is why:
"Depression is just anger without enthusiasm." (Best quote ever!)
What you're looking for isn't anger per se, but enthusiasm! Energy! Drive, and motivation to succeed!
If you can tap into that energy without getting angry first, I you're more likely to make reasonable decisions vs. rash ones (like biting off someone's ear in the boxing ring), and you're more likely to enjoy the event overall (once the intense anger is dissipated, you're left with -- yup -- depression).
What do you think?