I feel guilty for taking breaks during work

Recent grad and am starting the third week of my new job. I know no one is physically watching me (unless they stalk teams) but even just a quick break to go downstairs and fix myself a snack has the back of me saying “this adds more to the time you have to make up”. I still get my work done, early even, but I have this nagging thought of “you need to always be doing something when you’re on the clock” or “don’t leave your workstation”. Any tips to help alleviate this for an aspiring young professional?