A tactic I sometimes take, is to let myself notice the overwhelming feelings - I may even wave to them or say hey there annoying overwhelming thoughts 
Then I will invite them all with me to a mindful activity. Like I may bake something all the while letting those thoughts and feelings just be there, playing along to their tune....while I activiely engage in something that has helped me be mindful before.
Sometimes the cookies are all baked and I feel even just a little bit of relief for giving myself a mindful moment regardless of how crappy I may have felt. Getting that body moving, or the eyes looking - its hard but it can draw our body away from our mind and keep us a bit better connected to rationality.
Being mindful, won't always be fun or joyous, but it can still be helpful - if that makes sense!