"God, grant me the serenity to accept the things I cannot change,
"The courage to change the things I can
"And the wisdom to know the difference."
The wisdom to the difference is lacking for many people. Most people content themselves to suffer with nasty or unfulfilling conditions, or they attempt to change everything, and when so much has been changed to little effect, they change more things, with even less to success to show for it.
Acceptance indeed is the answer.
It's a good start, at least.
It is what it is. When a situation is goes sorely against the grain of an individual, chances are that person has not come to the place of accepting it.
Acceptance does not mean that what happened is OK, nor is it a sour resignation to make do with less than one would like. But it permits an individual to let himself off the hook. "I should have said, done, thought this." Well, you did not, and you cannot undo what you started.
But that does not mean that it cannot turn out for the best. Acceptance means that I individually cannot do anything, nor need to do anything more about a matter, but Someone else will!
"And we know that all things work together for good to them that love God, to them who are the called according to his purpose." (Romans 8:28)
"Casting all your care upon him; for he careth for you." (1 Peter 5:7)
I used to believe that God could and would if He were sought.
Now I know that He can and does, and all I have to do is receive it by faith!