Quote from illiquid:
The only way averaging down makes sense to me is if the total position was already considered as one position with staggered entries; that is, you knew you were going to go in piecemeal from the beginning.
Those that just throw on extra units just to bring down their avg price and raise their chances of just getting out even are building a habit of one day inviting disaster. In this case, there is no logical reason to connect your first entry with your second; the second entry is only a "good idea" if and only if it stands as a good trade on its own. You can't justify any losing subsequent entry just because it was at a much better price than your first, but that's exactly the reason it's so easy to give into the impulse for adding. But the sooner you can wipe out mentally where your first entry was and not let it impede your outlook for the second, the better; the market doesn't care and nor should you.