You can ALWAYS be forgiven! The only unforgivable sin is despair and thinking you can never be forgiven. (Look at Judas…) You don’t have to commit suicide to be unforgiven (and not all suicides are unforgivable…God is the only judge of what’s forgivable or not!!!), you can die of natural causes; but if you go thinking you can never be forgiven, you’ve literally shut the doors on Jesus and there’s no way He can forgive you. Don’t despair! Trust in Him!
Another point I’d like to make is good ol’ habit of making “deals” with God. Don’t promise God that you’ll get over your sins (or say I’ll do this God, if You do that for me). We’re born sinners. Promise Him that you’ll do your best to love Him and serve Him, and that you’ll continually try your best. God loves it when you’re able to pick yourself up and continue trying to do His will. He is forever patient, merciful, understanding, and loving!
What I’d suggest with the cussing is this: Turn it into something good. If you say “D*mn…” finish it with “…the devil.” Or something similar to that. Or either that get a jar, and put a quarter in for each time you slip. Use the money for some sort of tithing or to treat your friends in someway. Either way, you still need continue to confess it and try to conquer the habit. God will reward you for your continual efforts. And remember, change isn’t always sudden. A lot of times it’s gradual.
I’d suggest getting the My Daily Bread book by Anthony J. Paone, S.J. It will be able to assist you.
God bless.