If you are a trader, then red periods can be very lucrative. But if you are a long-term holder, then so long as you still beleive that the coins you have are for strong projects, then you should be fine. Crypto as a whole is still growing, it's just that there are plenty of downs as well as ups along the way. Yes, marketcap is very low compared with January - but it is hugely higher than this time last year.
I completely agree - as long as you have invested wisely, you will be ok. Especially if you're investing in a project with a revenue/ reward sharing token and the project is strong.
Also, my advice is to not sell at a high loss - if you're losing anyway and it's an affordable amount, keep it, to see how the coin will turn.