Ooooh, I heard something on the radio ( on my drive into town which can bring on negative thoughts , as I get grumpy about how far out we live!) yesterday about this. They said to think of negative thoughts like a channel on the tv. Don't try and turn it off, but just change the channel! Don't dwell on negative but find something positive to dwell on.
I see his as meaning don't dwell on my negative aspects but dwell on my positive. I find the more I focus on the positive , the more positive there is to focus on. KWIM? And perhaps by focusing on positive I can improve my negative.