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The concept of redemptive suffering is not at all masochism. It's genuine suffering in hope that one's suffering is redemptive for someone or something (e.g. a cause). This is the best analogy I could think of: a patient who is in pain is given painkillers, instead of using all of the painkillers he or she chose to save some of the painkillers for another who is in pain. So this is what happens with redemptive suffering, a person who suffers receives grace (which is unlimited by the way) from God and allocates some of the grace he or she receives for another person or cause, in hope that it will benefit somehow.
Any sort of suffering is redemptive, be it being caught in a jam, a toothache / stomachache / backache, the sweltering sun or even the bicep curl repetitions at the gym! Of course the amount of grace received is in proportionate to the amount of suffering one has to endure, simply because the capacity of receiving grace has also increased.
So the next time you find yourself cold and wet in the pouring rain, don't complain or grumble, offer up your suffering to God and for the benefit of someone (e.g. a friend) or a cause (e.g. the end of corruption). Frankly, I do not know how much grace I receive when I offer up my sufferings but one thing I know for sure, that whatever scraps of grace that's being conveyed to the cause or person will benefit somehow.