I tested at 7DPO...

Sarah
...and I am very happy I did. It was a negative, I knew it was highly likely to be a negative. But I still tested. I tested because if I waited that much longer I would have been that much more disappointed. I will retest in a few days, and again if AF doesn't show on her day and am okay for the results to go either way. I have mentally and emotionally prepared myself. 
If you want to test at any time, go for it. As long as you're prepared, then go for it!