Every investor have their own belief and thesis towards each investment.
Every investor have different risk appetite and guidelines to evaluate an investment.
Just before anything. Do you know why you’re investing for? 
Make sure it’s not because your friend told you so. Your friend might be providing you with one of the answer towards your question. But I’m sure that’s not the only one.

Let’s go into the topic now shall we?
Do you know why prices goes up or down for the assets? This is due to people buying and selling. Simple isn’t it? In every transaction out here, each buying order that is filled will mean that someone is selling. Those that are buying would have just entered the position while those that are selling have just exited the position.

When you exit your position, does it signify that your thesis have been met or this particular asset is currently over-valued? If so,