Use of Stop Loss depends more on your Investment Strategy rather than market conditions. If you are cautious trader then use of Stop Loss is always recommended no matter market is going up or down because crypto market unlike traditional security market is highly irregular due to non-regulations and small spread. So any coin can pump or dump anytime due to hundred of reasons. However, most of the traders don't use Stop Loss as crypto market is market of risk and patience. So even if your coin falls below your estimation, keep HODLing it and eventually it will go up as crypto market has tendency of upward movement in long run.