It seems like a banal recommendation:
Lock the screen (e.g. WIN+L in Windows) and lock the office,
when you leave your workplace. You should get into the habit of doing this for several reasons, even if you only leave the workplace for a short time:
With fundamentally practised behaviour, it is not perceived as a burden because performing it is perceived as normal.
Since IT security concerns everyone, you are a role model for yourself and also for your colleagues.
You make an attacker’s job more difficult if he or she cannot rely on you not locking the computer on the way to the coffee machine, for example.
You reduce the attack surface by reducing the possible opportunities to successfully gain access to your user ID/computer/data.
Target people you do not know.
Further advice on how to behave can be found in the letter from GB3/Abt31 dated 06.09.2011 “Security of official buildings in the TU Braunschweig area”.
Reference is made here to the statements of GB3 on security in official premises and the statements of the data protection officer, which are repeated every few years.