St. Ignatius, writing to Jesuits in Portugal, about the problems with spiritual disciplines that he deemed excessive:The first is that God is not really served in the long run, as the horse worn out in the first days does not as a rule finish the journey, and thus it happens that someone must be found to care for it.
Second, gains that are made through such excessive eagerness do not usually endure, as Scripture says, wealth gathered in haste will dwindle [Prov. 13:11]. Not only dwindle, but it may be the cause of a fall: and he that is hasty with his feet shall stumble [Prov. 19:2]; and if he stumbles, the further he falls, the greater the danger for he will not stop until he has reached the bottom of the ladder.
Third, there is the danger of being careless in overloading the vessel. There is danger, of course, in sailing it empty, as it can then be tossed about on the waves of temptation; but there is also danger of so overloading it that it sinks.