I know that guilty feeling all too well. It is important that you try and avoid that self condemnation though. Everyone messes up (addicts or not). So what? Move on. You can make that choice again to stop. There is life without acting on whatever we are addicted to. Try going to an NA meeting to get your head clear again. There are plenty of people that you can surround yourself with that have made that mistake over and over again until they reached their destination of abstinence. Try getting yourself around other people who you can relate with. Being alone with the guilt brings us down and interupts the process towards abstinence. Try calling someone if you can. Don't dwell on the call; just do it. (I always have had trouble with that and learned to just pick up my list and dial a number or two until I found someone.) I also started calling the local Crisis Line to talk to someone too. I often had really good listeners on the end of that line!!
Please, try not to let the guilt consume you. You made it 8 months!! Getting to abstinence is often a process. You can do it if you keep trying.