There is an oft-cited aphorism: you should sell at prices you would not buy at. Such "advice" has limited utility in practice because it contradicts another frequently-discharged gem of wisdom: let profits run.
There is no robotic algorithm for selling
Whether one should lock in capital gains, or wait for a multi-bagger, a useful consideration here might be the type of asset you are invested in.
If it is a growth stock, it may be worthwhile to "let profits run".
If it is a blue chip stock like a bank or telco, you may want to lock in some profits and wait for market cycles to work in your favor.
On the other hand, REITs rarely experience explosive share price appreciation by the nature of its business model. Hence, when there is an appreciable capital gain, ...