Do These Verses Contradict “Once Saved, Always Saved”?

Questions about whether Revelation 2:1–7 and Colossians 1:21–23 can be reconciled with a belief in “once saved, always saved.” 

• I’ve always believed “once saved, always saved,” but passages like Revelation 2:1–7 seem to say overwise. What am I missing?
• How does one reconcile Colossians 1:21-23a with the teaching of “once saved, always saved”?