I kept a bit more than 4% alts, since I managed (way back) to trade the majority of them into profit, meaning the ones I've kept are at zero cost. 

Last bull run, I didn't sell my BTC, I sold alts for BTC and cashed out some $ that way.  So, it didn't particularly worry me to keep them and wait for the next 'alt season' this time around.

Yes, they have increased in $ terms, but I still feel I lost out by not flipping 'em over to BTC when I should have, of course. 

Rationally, they have still made more money than I could have made on anything else outside of crypto. So I know I really cannot complain.  But irrationally - knowing how much more it 'could have been' makes it a strangely annoying place to be in.

I guess it's proof of loss aversion theory; we all fear losing money more than we enjoy making it.