As a person who fucked up their credit and then turned around and fixed it within 5 years, I've got some insight on this for those already behind the 8 ball.
I've always had a good, well paying job since graduating college in 2000 but I've always had a problem with discipline and just not giving a fuck outside of work. I liked to travel, I loved to get drunk at least 4 times a week, and was constantly getting in trouble for stupid shit with the law. The fines add up and so did the bills. I ran up my credit card bills got behind and my score dropped. They'd call and harass me for the money and I'd basically say "Fuck you, my score already sucks. What more can you do to me?" and hang up.
2004, I ignored letters from the courts. Fuck that, I ain't paying shit. Months after the letters, I go to the ATM and it says nothing is in my account. Shit. I go inside the bank and the teller tells me my account has been hit by the county. Their timing was perfect because it happened right after payday. I literally didn't have a penny to my name. I had to borrow a few hundred from my friend till my next paycheck. My credit score was like 480 or some shit.
That was the turning point. I called whoever I owed money and got put on a payment plan. If you do a payoff with the credit card , you can settle for as low as 35% of what you owe. So I settled like this where ever I could. I stopped drinking so much, stayed out of trouble and focused on my finances. About 5 years later, my credit score was 720, I didn't owe any credit card a penny, and in Nov 2009 I bout a $245,000 house on my own with a good interest rate. The only issue I had getting a mortgage was getting some paperwork from the county and DMV about liens that I paid off from my fuck up days.
I wrote a lot but my point is that you CAN fix your credit if it's already fucked up. I know when 1st hand when you're in the shit, it's tough to mentally get out of the shit. It may feel hopeless but the sooner you start the process, the sooner you'll remove the burden of debt and the have freedom that comes with being out of the shit.