What did John mean?
19: They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
1 John 2:19
What did Peter mean?
10: Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall:
2 Peter 2:10