I find challenging negative thoughts very difficult. The idea seems great when I am feeling 'up', but when I am in the grip of my old dark demon the last thing I can do is step back, be objective/rational/compassionate, and challenge how I am thinking and feeling.
My negative thoughts are generally about myself, my life up to now, my shortcomings of character and strength ... all that tiresome stuff. When I'm in a blue, it seems as if I am thinking clearly, and that there is abundant evidence for what I am telling myself. Very hard to challenge what feels, at the time, like cast-iron and self-evident truth. I suppose it is the self-loathing that grows from this hyperawareness of my own imperfections and failures that I must really challenge and beat.
I think I must acknowledge, not deny, my shortcomings and imperfections, but find a way to stop hating myself for falling short of what I think I should be, a way to accept myself for who I am, as I accept others. I'm nowhere near as critical of other people as I am of myself, don't expect others to be without faults, but I find it hard to forgive faults in my own self.
Shades of grey, must accept shades of grey, not just black and white.....