Most of the sugar people take in isn't the sugar they can see. It's dissolved into soft drinks and juices, layered through cereals, yoghurts, sauces, and packaged snacks, and folded into food that doesn't even taste especially sweet, which makes total sugar easy to underestimate.
Sugar isn't something to fear in small amounts, and it's a normal part of many foods, including whole ones. It's worth drawing a line, though, between the naturally occurring sugars inside whole fruit and plain milk, which come packaged with fiber and nutrients, and the added and free sugars concentrated in processed food and drinks. The concern sits mainly with the latter, because a consistently high intake is associated with weight gain and a greater risk of tooth decay and type 2 diabetes over time.
A useful ceiling is 90 g of total sugars a day, the reference figure used on many food labels. Be especially mindful if you drink sugary beverages regularly, since drinks are one of the fastest ways to move well past the limit without feeling full.