Yes, you can do it when you bought a coin. Logically when you have a coin it means you can do anything with your coin. You can sell them when you've got profit and you can sell them when the coin price is decreasing. You can set it, have you know all the feature in coinbase pro? I suggest you can see in some youtube channel to do what you want.

This is what I've done so far, I mean if I found new exchange and interest to the exchange I'll see in some youtube channel for all feature that has offered by the exchange and that is very needed especially if you have intention to be a trader. Also,you may need this thread because I think this is a useful thread to know where you have to put the stop lose when you bought a coin/token https://bitcointalk.org/index.php?topic=5261095.0