I was locked into a bunch of alts and didn't sell at their recent peaks because silly me thought they would be able to fight against BTC's influence.
Also, this is right around the time Cyrptoverter's alt signals went from runaway winners to suck-ass losers due to the BTC bear market.
edit: I should've sold all my Burst and Siacoin when I had the chance and put them into better alts.
edit2: Also, another thing that's annoying is even if I sold those alts at their peaks they would've ended up back into BTC because BTC trading pairs are what I'm the most comfortable with. Plus, all the Tether FUD was making me not want to put my satoshi gains into it to maintain my USD value for fear that it would all vanish over night.
edit3: another thing, it doesn't help that I work full-time and have to maintain a normal sleep schedule. So I can't be sitting at my computer looking at charts all day making sure I'm buying every dip and selling every peak.
Hell, I'm usually asleep when most of the action is going on.