I am sure that all people who reach a certain spiritual level, come to this understanding of human suffering--but amazingly, despite my advanced age, I am only just now realizing this: God allows everyone to have a certain amount of suffering--and to reach His Kingdom, we must willingly embrace it, if we wish to be perfect. Not conquer it, but embrace it, just as Jesus embraced his suffering on the Cross.
For some, it might be a life of material poverty. For others, it is physical illness or some kind of disability, or a person who never finds their soulmate and maintains a life of chastity despite their own deep desires. Perhaps it's the loss of someone that a person loved so much, life seems unbearable without them. It could be the misfortune of being born in a country which has great economic or civil strife, such that they experience the stress and uncertainty of immigration or becoming a refugee, leaving behind a homeland that should have been their safe haven.
It doesn't matter what it is: there are a million varieties of human suffering, but all have one thing in common: if you are so much in love with God that you wish to be perfect, then "deny yourself, take up your Cross and follow Me." (Matthew 16:24-26)
Understanding this--at last!--has been an incredible liberation for me, because it explains and justifies what is wrong with this world: it's the one thing that makes everything else make sense. All my life, I have felt guilty (for example), that I am not poor... that I am not disabled... that I live in the United States instead of somewhere else--and I am freed of that guilt now! They have their suffering, and I have mine: and it is all according to His plan. Nevertheless, this knowledge does not absolve us from doing everything we can to relieve suffering wherever we find it!
The challenge, of course, is the embracing part, because it's human nature to want to avoid suffering. And so, most of us spend a great portion of our lives struggling to escape from our suffering, not realizing that the only true freedom comes with acceptance, with offering our suffering to God in union with Jesus Christ. This is a mystical concept that not everyone "gets," but I am absolutely convinced that it is true.