Do, mean, etc. something for the best
Definition 1 of 1
Pro Tip 1/3Good Intentions
The phrase implies the person is trying to help, even if the actions might not be favorable to everyone. 
She sold the car for the best, thinking public transport would be healthier.
Pro Tip 2/3Unintended Results
Understand that actions done for the best may still lead to unexpected, sometimes negative, consequences. 
I chose the job for the best, but sadly it didn't work out.
Pro Tip 3/3Hindsight Explanation
It's often used to justify a decision after the outcome is known, regardless if it was good or bad. 
He didn't know it'd cause trouble; he meant it for the best.