Pocketing office supplies doesn’t feel like stealing, which is exactly how the habit hides.

Small thefts do not feel like theft because they lack every feature you associate with it: no victim in front of you, no amount worth naming. A pen goes in a bag the way a pen goes in a bag. What gets built there is not a crime but a threshold, and thresholds move: the pen, the ream of paper, the hours on the timesheet.

Decide the line now, while the stakes are low and a pen is only a pen. Put back whatever is not yours at the end of the shift. The habit you want is one that never needed a judgement call.