I've thought that before.... but when you see something falling and falling you start to question at what point to give up and cut your loses, even if that's absolutely the worst thing to do! e.g. ETH was down at $6 last year when all the fundamentals were great!
I believe ETH has a great future, but as a trader I'm not doing a good job if I take a huge loss even if it's just on paper, and miss out on an opportunity to buy more at a lower price. Not easy to do, but i do try to make myself start to sell off a proportion of holdings when things start to drop.
With SP, however, I can't do that - so I'll be holding, come what may, too :)