I too wrestle with the same decisions that you outlined above. Riding trends can be fun and exhilarating but buy and hold has worked for me in terms of separating a bit of that emotional element of trading (which gets me in trouble more often than not).

I like to trim back any positions that have a large gain, essentially taking my initial investment and playing with house money for the rest. This helps to manage the downside risk that the low-cap altcoins are famous for.