Everyone has their strategies. The important thing is to decide your strategy ahead of time to avoid emotional investing. The last thing you want to do is to buy/sell on short term emotions - that's how fortunes are lost.
My strategy has been to have a core position to hold (to riches or to rags) and have shares over the top to sell at peaks and re-buy on valleys. The risk is that if it keeps going up, I don't rebuy, thus missing out on all those gains. This is a risk I accepted and I balanced my core position to mitigate the risk. It has worked out pretty well for me but it might not fit someone else.
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