Barre chords can be tiring for the fretting hand. Strength is needed to hold down all six strings, especially when the remaining fingers are needed for additional notes. But often not all six string are needed under a barre, so try working on pressing down different combinations of strings. For example, when playing the C chord in bar 68 here you need only fret the sixth, second and first strings so the first finger can have a slight curve and press down in just two places; near the fingertip and the base of the finger. This requires a lot less pressure than pressing down all six strings.