When you start your script, a new process is created that only inherits your environment. When it ends, it ends. Your current environment stays as it is.
Instead, you can start your script like this:
. myscript.sh
The .
will evaluate the script in the current environment, so it might be altered
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…