This may sound strange but when alone or when my little one is sleeping I clean. I take an area of the house like my bathroom and start there. I shut my mind off and just do. If I'm really upset I'll scrub the hell out of my bathtub, slowly moving to other areas of the bathroom. Floors, organizing cabinets, ect. Shutting my mind off and moving slowly...by the time it subsides I will normally have an organized and clean space which will ultimately make me feel better in the long run.
If with my little one we take walks.. Normally after 20 minutes I have regrouped and have the attention to stop and play with him. This also makes me feel good.
I used to try and read but find it impossible to concentrate at these times.
I hope you find something that works for you.