Selling token at loss is not advisable but it still depends on what the market looks like. Sometimes holding when the market is looking bad isn't a guarantee that the token will moon later. Some coins I hold have remained stagnant while others even died off. So sometimes selling at loss is a good choice.
Everything we are talking about here is very relative. Yes, at the time of sale, the price of the token may be lower than the one for which the token sale was carried out. But if you sell token below this price and buy another promising coin, on which you can really earn money then the situation doesn't look so sad anymore. This I mean, you need to be dynamic and respond quickly. If you see an opportunity to earn money, then consider how to turn the situation around for your own benefit.