The refills you use are going to be positive thoughts, and will replace the previously negative ones. These positive thoughts will stop the negatives ones returning. Refill your mind with the thoughts you cherish the most. That wonderful holiday you just took. That happy childhood day. The encouragement from your boss about your progress on the job. That beautiful beach or mountain scene you saw in a picture. When your children were born. Everyone has a happy remembrance within themselves.
This happiness will gradually begin to replace the sadness and fear. Every time your mind flows back to the guilt and frustration, check it. No longer be a sleepwalker through your life, and allow your mind to fill up with unchecked thoughts. Become a deliberate creator of your life and consequent thoughts. Stop your mind drifting towards unchecked negativity, and use the power of deliberate refilling that will flow towards positivity. You will start to feel a lot more relaxed day by day.
Face those fears, and the reasons that led to your anger and that guilt. Yes, take responsibility for the consequences of your actions, but also realise that each person is making a choice at each moment in their life. You contributed to the problem, but not without the other person subconsciously making that choice and allowing it to happen. Now you know you're not the only one responsible, you can finally