#186-1. Any fool can criticize, condemn, and complain, and most fools do.
#186-2. The greatest lesson in life is to know that even fools are right sometimes.
#186-3. Action is the antidote to despair.
Criticism is constructive if its aim is to solve/improve and it is accordingly presented, preferably with suggested solutions wherever possible. Sometimes a criticism is countered with, "Why don't you try doing it?" but that is not a valid answer in all cases.
In a lighter vein, I would like to say, "Even Churchill is right sometimes!"
The third is good to remember in any "stuck" situation when further pondering is not useful. That is probably why Nike's tagline has endured so long: Just Do It.