opportunity

I received a message on my whatsApp. It says opportunity comes only once but misfortune keep knocking till you open your door so never forget to capitalize on opportunity.

I think all such messages are nonsense. Firstly, you'll always get a counter message or maxim which would convey a contradictory point.
For example, one would say humans are thinking animal. The counter point would say that thinking man is a depraved animal. One would say he who knows what is right will do the right. The counter point would say that its not about what, its about how you do it.
One would say, never ever ever ever give up. Other would say, happy people are those who knows when to move on.
One would say, honesty is best policy or honest people are the tallest in the queue. The counter argument would say, when the storm comes, the trees who doe not bend are often uprooted.
One would say, small is beautiful. Other says, size matters.

so ultimately what matters, which one is correct depends on your own perception and conviction. All such messages are nonsense upon stilts. They are good for confused souls. One who knows his priorities, likes, dislikes is well poised to reach the pinnacle.

Look at the irony, this also has the counter point, knowing is not enough. Acting on it is.