Hi Izzitme:Can you leave your desk for a few minutes to take a walk, perhaps along with some deep breathing exercises? I like the 4-7-8 breathing exercise (inhale to the count of 4, hold for 7 and exhale for 8, then repeat). I generally find that a walk can help refresh my perspective.
Depending on your work situation, you might have to improvise. If you can't go outside a building, maybe you walk up and down a few flights of stairs and/or walk around a few floors of a bldg. (maybe around the parking lot).
Another option, is to go to the restroom. Take a few minutes to just sit in a stall and do some breathing exercises. If you meditate, try practicing that for a few minutes.
If you can't leave your desk. Put on a pair of headphones and go to this Youtube address for a thought stream meditation. All you have to do is look at the scenes on the screen and listen to the audio. If you can't use your computer, you can use your phone. It can give your mind a little mini vacation.
https://www.youtube.com/watch?v=N0Lo5tUXkVI&t=170sA handy app to have on your phone is
"Insight Timer". You can get everything you need with the free version for Apple or Android. There are lots of options for different forms of meditation and relaxation exercises to help you chill out.
Hang in there! You can get through that presentation! Do your best to postpone your thoughts about your husband. As they pop up in your head, try to write down a quick note about the thought and then get back to the work you need to do.