A hydraulic machine comprising: a boom actuator comprising a large chamber and a small chamber , wherein the large chamber and the small chamber are defined by a piston movable within the actuator , the piston being connected to a piston rod that extends through the small chamber , wherein when fluid is received pressurized by the boom actuator and discharged from the boom actuator, an area on which fluid inside the small chamber is in contact with the piston is smaller than an area on which fluid inside the large chamber is in contact with the piston; a recovery unit configured to receive fluid discharged from the large chamber and then recover energy; a recovery line connecting the large chamber and the recovery unit ; an accumulator connected to the recovery line ; a jack-up assist line connecting the accumulator and the small chamber ; a jack-up assist valve disposed on the jack-up assist line to block flow of fluid from the accumulator to the small chamber in a first position and allow the flow of fluid from the accumulator to the small chamber in a second position; and a controller configured to control movement of the jack-up assist valve , wherein the controller is configured to: determine whether or not the hydraulic machine is in a jack-up condition; and when the hydraulic machine is determined to be in the jack-up condition, move the jack-up assist valve to the second position, characterized in that the controller is configured to determine that the hydraulic machine is in the jack-up condition when a load pressure applied to the large chamber by a load is equal to or less than a threshold value. a boom actuator comprising a large chamber and a small chamber , wherein the large chamber and the small chamber are defined by a piston movable within the actuator , the piston being connected to a piston rod that extends through the small chamber , wherein when fluid is received pressurized by the boom actuator and discharged from the boom actuator, an area on which fluid inside the small chamber is in contact with the piston is smaller than an area on which fluid inside the large chamber is in contact with the piston; a recovery unit configured to receive fluid discharged from the large chamber and then recover energy; a recovery line connecting the large chamber and the recovery unit ; an accumulator connected to the recovery line ; a jack-up assist line connecting the accumulator and the small chamber ; a jack-up assist valve disposed on the jack-up assist line to block flow of fluid from the accumulator to the small chamber in a first position and allow the flow of fluid from the accumulator to the small chamber in a second position; and a controller configured to control movement of the jack-up assist valve , wherein the controller is configured to: determine whether or not the hydraulic machine is in a jack-up condition; and when the hydraulic machine is determined to be in the jack-up condition, move the jack-up assist valve to the second position, determine whether or not the hydraulic machine is in a jack-up condition; and when the hydraulic machine is determined to be in the jack-up condition, move the jack-up assist valve to the second position, characterized in that the controller is configured to determine that the hydraulic machine is in the jack-up condition when a load pressure applied to the large chamber by a load is equal to or less than a threshold value. <EOS>