Always do a research first on the coins you want to invest and hodl, Coins with active developers and supportive teams will surely stay long in the cryptomarket. These developers keep upgrading or innovating their coins to meet the challenges that lies ahead thus keeping also their coin on the top of the market.
Projects that are working products and real uses, will certainly always innovate and develop projects. Then the analysis is very important to determine the right time to sell and hold. By understanding the roadmap, we will also find out the team's seriousness in developing the project.
It is meaningless to think about the loses. I don't invest in the small projects that never will reach the goal of the whitepaper. Projects usually have goals which they don't reach in the bear market and they take responsibility after blaming the bad market circumstances.