In 2010, you came across a site that was giving away bitcoins. The site said it was free money so you signed up. You were logging in to figure out how it was money but couldn't. The last time you logged in you had more than 100 bitcoins. Later you forgot about the site until 2017 when a ponzi was advertising Bitcoin. Bitcoin? The name rang a bell and you stated hearing stories. You remembered you must have many bitcoins somewhere but you can't even remember the name of the site. How would you recover your BTC?
That is why every action or transactions we've made should be put in a note. In my long time here in this industry I always keep saving a note where I used to sign up and the password even the username I've used on it. Remembering what website would really be a pain especially if you visit a lot of related websites. Actually, as you sign up on particular site, one of the requirement is your email so you could find what you are looking by just searching on your mail.