God doesn't just choose to be good, to avoid evil, to act morally, etc. God is holy. He is transcendent from those things—totally set apart and separate from them. It is not just some moral code or ethical law that we find in His law and commands . . . it is the very nature and character of Him. There is such a powerful realization in the truth those few sentences above contain. If someone simply chooses to be a certain way then there is always the option of them choosing not to be that way any longer. But when someone is that way—inherent in who they are, in their very being—and they are completely cut off from, and separated from, the alternative—then we can know with assurance they will always be that way.
The Apostle John tells us twice in 1 John 4 that God is love. It is part of who He is. It is not simply that God chooses to love, but that He is love, and there is a big difference. So, when we don't love another we are partaking in a something that God can't be a part of. He can't be a participant in, or an advocate of, or lend His hand to it when we don't love. So, while I know that He won't ever leave me, and that I am sealed in adoption as His child by my faith in Jesus, there is a sense that each and every time I don't love I am separating myself from God—or separating Him from what I am doing . . . not to mention I am not honoring Him by my choice to disobey Him, and I am failing to love one whom He loves enough to die for.
When I choose to not love another with a love that is patient, kind, not self seeking, not keeping a record of wrongs, not rejoicing in evil, etc., I am, in a sense, choosing to step outside of Him because, He can't be part of "not love" when He is love. I don't know the full "theological" implications (or explanations) of the concept I am trying to convey, but to me it is pretty clear that, up to the edge of losing my salvation, I am separating myself from God in those times (or at least moving outside of Him in my actions, or causing my actions to be outside of His cover and blessing and presence). I don't know if this is what the Bible talks about in quenching the Spirit and grieving the Spirit and things like that, but I do know that if I truly desire Him to be my breath and life, and to bear His image, and to have His voice and Spirit lead me, and to have Him work through me, then I must love. When I don't, in some way He pulls back, because He can't be a part of that because it is against who He is.
Matt 22:37-40 And he said to him, "You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. 39 And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets."
1 John 4:7-8 Beloved, let us love one another, for love is from God, and whoever loves has been born of God and knows God. Anyone who does not love does not know God, because God is love.
1 John 4:16 So we have come to know and to believe the love that God has for us. God is love, and whoever abides in love abides in God, and God abides in him.