Freshly juiced vegetables and fruits are extremely healthy due to the concentrated nutrients that you get from them.
However, it is not recommended to drink a mono-vegetable juice, like carrot juice. Vegetables should be mixed and then juiced, such as 1 carrot, 2 stalks of celery, some parsely, and some lettuce, etc. The juice should then be part of the rest of a meal, so that you also have fiber and protein to help with the absorption of the nutrients from the juice. You also need some good healthy oil. Vitamins A,D,E, and K are fat soluble vitamins and can only be absorbed into the body by fat.
Fruit juices do contain concentrated sugars. If you want to juice fruits, I recommend putting some aside so you can eat it with the juice. That way you get the fiber.