In my life experience, I have encountered many things that were too difficult for me to do. Whenever I have expressed my frustration to Christian brothers and sisters, they most generally say, "With God all things are possible," of course referring to Matthew 19:26. What they are implying is that if I were more positive and prayed, God would miraculously enable me to achieve the impossible. In other words, if I were more spiritual (perhaps like they were), I could do anything my heart desired. After all, didn't God say He would give us the desires of our heart (Ps. 37:4)? Perhaps I should be more optimistic and pray that I will not become so aggravated with my friends! Maybe that is how Job tolerated his "friends."
Never mind that the context of the Matthew passage has to do with people being saved, which is totally the work of God. Never mind that the passage from Psalms should be interpreted to mean something quite different from using God as a genie. To me, it actually means that if I delight in God's will, my desires will be like His. And, because He and I want the same thing, it is definitely possible. But there in lies the rub; it takes both God and me working together to accomplish the impossibles of my life. I, more often than not, fail to live up to my part of the equation. My human nature (sin nature) wants to "do its thing." So, because of my inability to continually live a spirit-filled life, I encounter real impossibilities.
My number one problem is, and has been ever since I became a Christian forty years ago, my inability to love others. I not only appear unable to love my enemies, I find it difficult to love "my friends." Oh, I do just fine when I meet new people, but before very long, they will demonstrate imperfection and will loose me as a fan. I know that I am holding others to a much higher standard than I myself am able to meet, and I realize the hypocrisy in that, but that is who I am. Disgusting, I know. Changing me definitely will require the work of God! I have tried repeatedly, but to no avail.
Having said all that, I would like to suggest that Romans 12:9-21 be interpreted in a similar fashion as one would interpret the Lord's teaching concerning legal justification for divorce found in Matthew 19:3-9. Because of man's inability to forgive adultery, God allows divorce. The real problem is unforgiveness, not adultery. In the Romans passage, Paul is instructing Christians on how to respond to others. After setting the standard (love them all), he adds, "If it be possible, as much as lieth in you, live peaceably with all men" (v. 18). I understand Paul to be saying we are in various stages of spiritual maturity, and we are to do the best we can to love even the "unlovable." The "unlovable" part says more about our inability to love than it does the character of others.
So yes, with God all things are possible, but we are not God. We are limited due to our sin nature and spiritual immaturity. To dwell upon my failure to love like God loves, is a demonstration of pride. Who am I to think I can love like He does? Oh, how I long for that day when I shall be like Him (1 Jn. 3:2)!