Christan, I understand what you are saying. It's hard sometimes not to let a cuss word come out of your mouth, or even a replacement word. It's especially hard when you get angry, lose your temper, or accidentally hurt yourself.
The problem with replacement words is that they are still cussing. They may not be the words that the WORLD has defined as naughty or derogatory, but to GOD, they are still just as bad.
God wants us to be clean, pure, as good as we can get, after all, we aren't perfect. But He wants us to try, and if we have cuss words coming out of our mouths, imagine how filthy we are inside. We are temples for God and need to stay as clean as possible for Him, inside and out.
So when you hit your thumb with a hammer, or if you blow your temper, and you need to release some steam, try:
"That hurt!" or, my favorite. "AAAAAAAAAAAAA!!"
or
"I'm so angry!" or "That makes me so mad!"
And work on cleaning up the inside as well. For the Lord and for you!