I think it depends on the type of sin and the reasons for it.

If one commits certain sins very deliberately and with malice, repeatedly, one can become reprobate.  That is the word you want to Google.  Reprobation entails the withdrawal of grace -- God leaves us to ourselves.  That is indeed a frightening condition.

However, sins of weakness, even committed repeatedly, are often used by God to bring a person to humility and make him more open to grace.  Recall what St. Paul wrote about the thorn in the flesh.  M. Eugene Boylan explains this very well in his book This Tremendous Lover.

It is said that one becomes holy either through great purity or great humility.  I know that for me, it will be the latter, or nothing.

Don't despair.  Remember what St. Alphonsus Liguori wrote.  No one who prays will be lost.

Take a moment to read the quote from Columba Marmion in my signature.  That's the key to your situation.

Yes there's a difference between sins of malice and sins of weakness.

So if you repent for a sin of malice then can you get back to where you were (with God) like before you committed the sin?