At the expense of dating myself, there is a children’s toy played with back in the day called “A Viewmaster.” You would place a round disc of small pictures on it into this plastic viewer, click a lever to advance the pictures around as you would view them.
The Stop Technique will have you select one picture (always the same one) of a happy remembrance you shared with your departed loved one.
When you are confronted with the negative image you mentally STOP that picture, insert the happy one, and concentrate on it.
For a while, you will have to force this however the more you do it the faster you will train your brain to do it on its own.
ALSO when you have this moment to enact this technique take a breath through your nose, exhale through your mouth, and this way you will begin to take control of what is going on inside you. This is called The BRA Technique-Breathe Relax Attitude. Many times this negative image surfaces when you are not expecting it and need to be able to have a different focus.
I hope this provides some relief for you if you have a need to adopt this as many survivors have commented positively about it when they have used it.