The third wave is typically long, obvious and clear. The psychology behind this can be summed up with the word greed. People are expecting massive gains in a short period of time. The sheeps have joined the flock, mums, dads, uncles and aunties are all talking about it.
Fourth wave is sudden and expected. The bulls are exhausted and the sheeps need to be taught a lesson. While it appeared easy to make money just by holding, the real test begins. Everyone knew how volatile Bitcoin is. Before buying, they will tell themselves they will hold for xx months/years and are strong hands. But when they see their investments drop from $10,000 to $8000, then $5000, and maybe even $3000, panic will ensure.