Allthough Teshuva is a good thing, we believe (by Scripture) that after Teshuva a person only receives forgiveness by faith in the atonement Yeshua HaMashiach brought by His Blood (Sacrifice).
1 Yonachan 1:5-10 (CJB)
5 And this is the message which we have heard from him and proclaim to you: God is light, and there is no darkness in him — none!
6 If we claim to have fellowship with him while we are walking in the darkness, we are lying and not living out the truth. 7 But if we are walking in the light, as he is in the light, then we have fellowship with each other, and the blood of his Son Yeshua (Messiah, the Anointed One) purifies (cleanseth) us from all sin.
8 If we claim not to have sin, we are deceiving ourselves, and the truth is not in us. 9 If we acknowledge (confess) our sins (in repentance), then, since he is trustworthy (faithful) and just, he will forgive them and purify (cleanse) us from all wrongdoing (unrighteousness).
10 If we claim we have not been sinning, we are making him out to be a liar, and his Word is not in us.