Here are practical steps that you can take to clear the slate:
Learn Humility: God is perfect. You are not. (Well, maybe if you're Donald Trump.) Therefore, you will make mistakes. Recognizing that you are imperfect is the first step. Because, if you don't have to be perfect to be loved, you can relax and focus on recognizing your flaws and growing. You will then get closer to being all that you can be.
Realize you did something wrong: You need to be aware of your surroundings. Your spouse may cry or become silent. The smile vanishes from their face. They start to yell at you. Since you are humble, you will learn to recognize when you mess up. Then, you can at least be happy that you have an opportunity to become better.
Admit your mistake to your spouse: Don't be shy. Your partner will admire your admission. They will also appreciate anything that you do to improve your life together. Besides, they know how you treat them. It is not like admitting your faults will be news to them.
If you are dealing with an issue where there is a secret that could prove damaging, seek professional assistance. There are different opinions as to the value of disclosure. But, in all cases, whatever you are doing that is hurtful to your spouse must stop.
Commit to not repeating the mistake: If you repeat the same inappropriate act you need to apologize again. But, it would be smarter to try and figure out what is bringing about your bad behavior. Do you have a personality issue to deal with? Anger, jealousy, cheapness, vulgarity and being condescending are examples of character traits that are difficult to live with. We all have our issues. But, what are you specifically doing or not doing that is having an effect on your marriage? Speak with your spouse. Learn to communicate openly. Ask your beloved what you do that is offensive?
But, obviously, you need to listen and not react with disrespect. With the information you gain, you can plan a step-wise program to begin the process of not reacting in that manner again. If your spouse can work with you to reward your changes, great. But, regardless, you need to make the changes anyways. It is far wiser to avoid doing something you regret than to keep apologizing for it.
If instead you are responding to circumstances, then much of the same advice applies. Speak to your spouse and try to brainstorm alternative ways of handling the stress. Are you part of a supportive network or community? Do you research on the net what advice may be out there? If both of you think that it is appropriate to your situation, then you have leveraged the wisdom of many people to your benefit.
Seek help if the problem is too difficult for you to face alone: People facing addiction issues or abuse issues, for example, will need to seek help. Do so! You have so much more to gain than lose.
Be as generous with your spouse as you want them to be with you: Life is about growth. Enjoy the progress you make. Build your marriage into something that you can truly take pride in.
You will feel much lighter no longer carrying the burden of years of pent up disappointment.