I can't count how many times I "screwed up" my sobriety over 29 years of drinking. I used to get drunk every weekend and then vow "never again", only to be right back at it the next weekend. Eventually, I just gave up and started drinking every day for 10 years straight. Finally, just over one year ago, I once again said "never again". This time I really worked on why I got drunk in the first place. I figure I worked hard all those years to stay drunk, I might as well work hard to stay sober. It hasn't always been easy, but it truly does get better and better.
I figure if this "hopeless case" can turn it around, then anybody can.