Notice the title says "Stop trying" because that's as far as you can get. You can "try" to fix people, but you will never succeed.
You will never succeed because you did not create the person. Therefore, you do not know how that person is wired. You have no idea about the person's inner workings.
When you try to "fix" people, you might think you are helping, but instead you are interfering in God's work. In essence, you are "hindering" rather than "helping."
God wants people to go through certain things so they can be strengthened for the tasks He has for them to perform. When you butt in, you interfere with the entire process. It is like trying to help a caterpillar through the stages of metamorphosis. If you interfere in the process, the caterpillar would never become a beautiful butterfly.
God wants to give grace so His power will be perfect in the person's weakness which you actually block. You are in the way of God's grace to be dispensed on the person. Since you don't have any grace to dispense, then step away.
But he said to me, “My grace is sufficient for you, for my power is made perfect in weakness.” (2 Corinthians 12:9)
Reconsider when you attempt to fix people. It might be you who need the fixing. You try to fix people to bring glory to yourself when all the glory belongs to God.
If you shouldn't try to fix a person, then what should you do?
The answer is simple: Turn that person over to God; then you get out of the way. Let God work with the person. After all, He can get the job done while you will fail every time.
[This message is straight from the throne room of God. Please meditate on it and forward to those who also might need this proclamation.]