Yes, but not permanently so because it is of their doing, not God's. There are many who presume themselves Christians but who have not been saved - their trust remains in themselves but not in Christ as the Saviour.
[Luk 8:13 KJV] 13 They on the rock [are they], which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away.
[Jhn 15:2, 4-6 KJV]
2 Every branch in me that beareth not fruit he taketh away: and every [branch] that beareth fruit, he purgeth it, that it may bring forth more fruit. ...
4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
5 I am the vine, ye [are] the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.
6 If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast [them] into the fire, and they are burned.