No matter how low a person may have fallen and no matter how severe the sins they have done, the doors of true T'shuvah are never closed and G-d's hands are always outstretched and waiting for us to return to him.
The main part of T'shuvah is to STOP sinning. The next step, is feeling bad for what we have done and asking G-d to forgive us. (But obviously if someone is not ready to stop, it doesn't help to ask G-d for forgiveness and it doesn't help how bad they feel).
From website www.HalachaForToday.com
I am to my Beloved [Hashem] and my beloved [Hashem] is to me.(Shir Hashirim 6:3).
Seek out Hashem when he is nearby, call out to him when he is near.(YeShaya 55:6)
Chazal tell us that the Pesukim above are referring to the month of Elul!
The 40 days from Rosh Chodesh Elul until Yom Kippur are a special period when Hashem is extremely close to us, and he is waiting for us to return to him, to do Teshuva (repentance) and to strengthen ourselves in Torah, Tefilah and Good Deeds. Not only is it important to grow spiritually in this time period, it is also much easier to attain higher and loftier goals than it would normally be during the rest of the year. Let's take advantage of this closeness to Hashem and become better Jews in all areas of our lives , and thus hasten the coming of Mashiach and the rebuilding of the bais Hamikdash very soon. Amen!