On Monday, the seventies pop icon pleaded no contest in a California court to driving under the influence (DUI) following his arrest in January.After receiving a sentence to serve 90 days in rehab and complete a nine-month alcohol program, Cassidy is ready to face his battle with the disease head-on after a troubling few years.In an interview with Piers Morgan, Cassidy admits: "If I take another drink, I'm going to die, physically, mentally, emotionally, spiritually. I'm dead. You know, they say it's a slippery slope."It's not a slippery slope. It's from 12:00 to 6:00 on the clock and the whole face is ice. One sip, one drink, because there is no such a thing, not to an alcoholic. You have one and you're done. I'd be done."The I Think I Love You hitmaker adds: "I am most definitely an alcoholic. And the interesting thing about it and the way you end up with multiple DUIs - I never got arrested for anything until I was basically 60 years old. I had been lying to myself and consequently lying to everyone else about my disease."The 63 year old's January arrest was his third DUI since 2010, but his troubles worsened in February, when his wife of 23 years, Sue Cassidy, filed for divorce.When asked how his drinking affected his marriage and its eventual demise, Cassidy said: "She'd (Sue) just say it made me an ass. It made me a fricking d**k (sic). I wasn't authentic. It's because I have an allergy to it. My personality changes I'm not aware of it. I never stop talking. It's obnoxious. It's embarrassing."But the singer is hopeful for the next phase in his life, recalling the "spiritual experience" that completely changed his attitude on the future of his well-being.He explained: "I dropped to my knees and I felt something go through me. I felt this experience that was just, thank you God. I felt this relief. I begged it and I was crying and weeping like a little boy, like a sobbing little infant, like I'm sure I did many times as a kid. And I felt this incredible sense of relief because I stopped lying to myself."