I think so many times when we face challenges like this, that instead of always looking at the challenge and getting frustrated because of the way they are we should look at ourselves and the way we are. Maybe sometimes God is using these opportunities to refine us. He's making us a better person through the challenges we face with children like these.
I don't blame Joshua for his behavior, I also don't accept his temper tantrums or misbehaving as acceptable behavior. I deal with the issues at hand, but I pay close attention to how I deal with them.
My Bible tells me that love is patient, kind, not rude, not self-seeking, not easily angered, keeps no record of wrongs, always protects, always trusts, always hopes, always perseveres and NEVER fails. It also tells me that I should have love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. That those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. And that since we live by the Spirit, let us keep in step with the Spirit.
So I take these words as a challenge for me to keep in mind as I raise our children. It's easy to get angry and discipline harshly, because it's what my flesh feels like doing. It takes a lot more self control to discipline in love. But I can guarantee you that the outcome will be so much more worth it in the end. Besides, if I think about it, isn't God patient with me? My strong will may not be as obvious as my two year old's but how many times has God gently and loving taught me the same lesson again and again when I stubbornly do the opposite of what He tells me?
So love those challenging kids of yours. No one said parenting was easy, but if you do it God's way it's soooo rewarding, for both you and your child.