Take your time first to think about everything before selling what you're holding just because you see the prices surging, ATH may bring good fortune to those who got the patience to hold in the bear times but I suggest that if you don't have any rush needs or some plans ahead, just hold it until the next ATH will come so that you can acquire more profits. Just take a little bit of what you've earned because as you've said, this is your first bear market. Anyway, it's your option because it's your own coin.
If he holds BTC and ETH it is better for long term investment but if he increases assets then must buy at lower price than current price, top coin market will surely increase again during bullish season, I have both coins in portfolio at the moment even though it has suffered losses due to the market correction but I am still optimistic that the top coin price will reach the ATH price in the next few years.