FWIW, B-complex is helpful in negating some of the physical effects of stress. They are not fat-soluble, meaning you can take higher doses than the RDA safely.
Exercise has always been the best way for me to relieve mental stress.
I like the multi-vitamin/mineral products made by this company:
The vitamins are in easily digestible capsules, not tablets. They offer other products as well that are supposed to help negate the effects of stress - herbal 'adaptogens' and others. I can't comment on those because I've never tried 'em.
Hope this is helpful.