I do agree with this but also the price for Bitcoin, ETH anything really is reliant on US dollar and perceptions that also go with that.   What can appear as weakness in the price can also relate to flows in the dollar between nations of the world, the Dollar index has recovered some this year in 2018 where in 2017 it mostly fell almost as a certain trend the whole year.

That recovery for US dollar is seen as lower pricing and possibly also demand in usage of BTC.   Longer term I do think the dollar index will continually fall until they solve a budget deficit and are able to tackle their long term debt overhang on the economy.   Crypto is not likely to be reversed to nothing as almost every participant acknowledges, however some think the technology can be centralised and controlled by one entity with value dictated rather then a free market with decentralised processing.    
The price variation is partly on confidence which protocol will do best but also about development still ongoing by those competing for the market revenue I think.

  I would advise not to wait for a bottom price or a top price, spread out your buys and sells so you can last the distance like a marathon.  The factors to success are far beyond us as individuals, past the horizon we see and so we must last till this whole process of change is clearer to far more people then just us on the forum discussing hopes and dreams