God neither has needs, nor is He driven by necessities. If we follow Christ, we will feel a need to confess our sins, not as a legalistic obligation, but as a realization that we have been ungrateful to Him.
I'm sorry, I meant is there a need by man to be forgiven of sin by God for salvation? I thought I remembered that actually achieving theosis is rare for someone, at least in this lifetime, but that it was still possible to be saved. I was trying to ask how integral is God's forgiveness of sins to this? I guess I mean is God's forgiving of our sins one piece of a larger salvation puzzle, or is it absolutely key?
Theosis is becoming God-like, Christ-like. It is a process, a spiritual growth to holiness through faith in God, in due time.
You may have heard people of my faith say things like they want to adopt "the mind of Christ" or that we should "conform ourselves to the image of Christ". Are these comparable? Also, theosis sounds a lot to me like what I would call sanctification. Is this right, or are there important differences?
Sin is spiritual dirt we continue to cover ourselves with no matter how much we love God. We do it daily, hourly, every waking moment. Yes, there is a need for us to become pristine in order to be in communion with Him, so the answer is yes, our sins must be forgiven; we must be cleansed of all that separates us from Him. Some of that we can do ourselves, but ultimately it is God's mercy that accomplishes that.
You may have heard people of my faith say things like they want to adopt "the mind of Christ" or that we should "conform ourselves to the image of Christ"
That's part of it FK. Theosis is a way of "life in God." It is a process, a struggle in fact (Slavonic word for it is podvig), because our sin-prone nature makes it a struggle. It involves placing God first, everywhere and all the time and denying yourself. The idea is to become pure and clean so that, to paraphrase the Scripture, His light can shine through us for others to see and know Him.