Yes that's effectively what happens around resistance levels. Milestones may be psychological resistance levels. People may have common and similar milestone targets that they all want to sell at (every 1,000, 5,000, 10,000 etc..) ..there is a sell off until more new buyers come in and have an opposite reaction of seeing BTC hit a milestone target and not wanting to continue to miss out.
Yes trading is difficult and it's probably better to just be a very long term holder. I'm sure many people who got BTC when they were 5 cents sold them off when they were over a dollar and even more sold when they were tens of dollars .. it's probably better for people to forget they even have Bitcoin on their computer and remember years later.
I think that is very sound advice. Cannot underestimate some understanding of human psychology.
Your second part is exactly what I did with my first bit of Bitcoin. I got it at about $50 and sold when it first hit the $1,000+ range - I was able to catch it at about $950 as it came down. I have that paperwork I wrote for that Bitcoin framed in my office as my most valuable to date work. lol A reminder of sorts.
Now my wife and me put money in Bitcoin as a "last chance" rainy day fund. This has only bit us once in several years where Bitcoin had dropped from about $2,300 to $,1900 at a time we needed it. Those are some great odds in my opinion.
Now we simply forget we have it until we need it. My shift card stays hidden out of sight and only comes out when we need it.
Great job HODLing!