Edited: this is an advise to investors not day traders, findings have shown that day traders don't live long and majority of them develop High blood pressure over time.
Whether traders or investors, this advice is easier said than done. The reflex to always take a peep in one's object of interest shouldn't be seen as a bad practice. This is normal and people should indulge it if they so desire. I used to be caught up with that anxiety in the past but I am a bit relaxed now checking it. This is a beginner's undoing most times. For instance, there was a time one could check price and felt it was going down only to sell off and price rebounds to a higher high. But if one didn't anxiously check it at intervals one wouldn't exit the trade at such a time.