Bresson believed that photography was about capturing the perfect, decisive moment. It was spontaneous, yet planned as he would sometimes observe his subjects for hours before taking his decisive shot. I believe this approach is very interesting and has merit in the sense that capturing your subject in their natural environment and producing a a viable interesting piece is a very difficult thing to do in one shot, but the payoff of a successful shot of a decisive moment is well worth it, because you can capture some truly authentic moments that really add emotion to your piece and captures the human experience in a way that can have way more substance than your typical portrait or candid.
He may have observed for hours but he is known for taking a lot of photos and capturing a special moment. He had a lot of not so great pics to get to the truly great ones. Work the subject and be ready for the moment