^ nothing to feel guilty over to be honest. The more guilt you feel, the worse self-esteem, the more likely you are to relapse; maybe not every addict but more often than not, using their DOC reinforces their self-esteem/feelings of happiness, etc.
It's better just to admit that you fucked up, or slipped up, however you want to put it, and that you still have the rest of your life to get back on track and you can get back on track in no time. It's all about will power and determination. It takes just as much will power and determination to relapse/use in the first place, it just takes a changing perspective of what you want for yourself to shift gears into getting better.
It's also important to address why you are using, and to make sure that you feel good about yourself without drugs. It's good to forgive yourself for things you have done in the past - as long as you have learned from these experiences. In this sense, there's no reason to feel guilty about using or a relapse, as long as you are making the progress you need to recover.
Some people have posted the idea before that relapsing can be part of a recovery, sometimes using the drug again can have negative effects from too intense of a dosage or from side effects, etc. - eventually the person can be put off from using it due to experiences like this (it has happened to me).
Another word of advice to everyone here trying to taper on Suboxone or to get off it/opiates all together, make sure that you have an active life outside of drug use, including having sex, exercising, eating well, taking good care of yourself, having hobbies/activities you enjoy, socializing with friends and family aka your support network, etc. It's also a great idea to have someone know what you're going through; have a small group of people who are understanding of what you're trying to accomplish for yourself, and can help you out if needed.
I just wanted to share all of this because I have been doing incredibly well for myself cutting back on Suboxone drastically, and I am planning to be off of this drug eventually.