Christians still sin but we are not forsaken

"The adultery of David with Bathsheba is an example, not to move us to evil: but if (while we follow the way of righteousness) any chance drive us aside, that we despair not. For if we saw not such infirmities in God's elect, we which are so weak and fall so often should utterly despair and think that God had forsaken us." - William Tyndale, the Obedience of a Christian Man, pg. 163


I remember once talking to an old friend of mine from Southwestern. He was a Lordshiper who said that if we sin then it shows we were never of Him. I tried asking my friend for clarification. He kept saying the same thing every time I asked. So the conclusion is that he must have meant every word. This is the conclusion of Lordship salvation or legalism. If you sin once then you are not a Christian. However this not what Tyndale said. To be a Christian is a spiritual matter not a physical matter.