Yeah. If you try specifically not to think of a certain thought then it tends to make the thought worse (an ironic process).

I guess it would be good to have a number of strategies in your tool kit so you could try one and if that doesn't work then move to the next one on the list etc.

I guess you have
- distraction (alternative stuff to focus on)
- using it as a basis for more positive thoughts
- acceptance
I wonder what else you could try...

Something I do is mindfulness meditation to focus on my breathing. If I focus on how my breathing *feels* then while thoughts occur to me I just gently refocus my attention back on my breathing. It kinda works for flashback type memories... I wonder if it would work for your thoughts? I guess this fits under the header of distraction...