The affect heuristic is BAD.  It is NOT GOOD.  You should AVOID LETTING IT CORRUPT YOU. 

Seriously, though, jokes aside –

One of the most useful mental-discipline techniques in the toolkit is “try as hard as you can to learn about something before you decide whether it’s good or bad.”  I’ve found that a reasonable rule of thumb is “know at least four concrete things about the topic-at-hand before you start generating normative conclusions, and if you find yourself generating normative conclusions before that point, quash them ruthlessly and apply the operant-conditioning Failure Stick.” 

Needless to say I do not always do this successfully.  But when I do I’m generally very glad of it.