"Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allāh. Indeed, Allāh forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" (Az-Zumar:53)
Your sins are nothing comparing with Allah's vast/wide forgiveness, just you should know that He is the forgiver and ask His forgiveness. I heard in a hadith that someone make sin and ask Allah's forgiveness so Allah will say to His angels; my servant commit a sin and knew that He has a Lord who forgive/punish for sin and asked my forgiveness so be witness that I forgave him. and once again and thrice until Allah will say "I forgave to My servant, so let him do whatever he wills".
"Repent" means; leave the sin behind and return to Allah with an intention of not commit it again, or escape from your sin and turn to Allah.. if someone repent and then sin and repent and then sin...etc. Allah will not stop forgiving as long as he/she are still alive. Just shaytan/satan will despair from such a person because whenever he whisper him to do sin he return to Allah after with clean heart/intention and Allah is forgiving and accepting of repentance.
the most important is that you keep humiliated/broken and in need of Allah all the time. whether you are doing good or bad deeds.. I mean the sinner who seeks the need/help/mercy of Allah is better than someone who is doing good deeds and think it will make him free of need from Allah. because we enter Jannah by Allah' mercy and not because of our deeds.. so we should always seek his forgiveness and mercy.
good deeds are effecting our heart with light and sins are effecting our hearts with darkness. and good deeds erase the bad ones.. I hope you start step by step by avoiding two bad deeds and do two good deeds but on the term that you should keep them and after you be strong avoid another two bad deeds and start another two good deeds until you be strong and so on. just keep a relation with Allah He is nearer to you than anything.
There is a layer of darkness at the bottom and a layer of light at the top and a layer in between in the middle try to let your heart realize the difference.. and ask the help of Allah as He is the one who take us out from darknesses into His light.
and for more information about your self please read the following details;
prophet Muhammad salla Allahou 3alayhi wa sallam called it the bigger Jihad/fight/struggle. And first step in these battles is to "know thyself".. as our nafs is considered an enemy from inside(beside the famous enemy shaytan and beside this world and its fancies) until we control, purify and educate it. so in its first stage it is called Nafs ammara bessou2(a self ordering evils), As in Quran; "..indeed the nafs/ego/soul/self is a persistent enjoiner of evil, except those upon which my Lord has mercy.."(12:53) and after it see the light of Allah it will become a better stage/rank called Nafs lawwama(a self which blame him/her when he/she falls into sin or error.. as in Quran "And I swear by the reproaching nafs/soul/self."(75:2).. and there is other higher ranks after that, one of it is the nafs al Moutmaenna(or comforted self) as in Quran karim " O reassured/comforted nafs/soul. Return to your Lord, well pleased and pleasing(to Him)."(89:27-28)
Note that we are consisting of two totally opposite things; the body and the spirit. the body is made from earth(dust,water,fire and air) and its food, life and death is from the earth.. while the spirit/Rou7 is a matter of Allah that is why its food and life and death is in its relation with (light of) Allah. while the nafs/we or call it the heart(which decide our deeds) is like a mirror that has no color but it takes the color of what is in front of it.. and in front of this heart there are two doors; one is the door of this world and another door is the Afterworld. As our hearts are between two fingers of Al-Rahman he turn them as He want.(between this world and the afterworld or between the Body and its request from world or the Spirit and its request from Allah's light or between a group of angels inspiring to us or a group of shayateen whispering to us) the heart/nafs in the beginning is busy by the affairs of this world(of course because it knows that no food means death for the body)(but it got the real knowledge it will depend on the one who provided, guarded and guided it while it is in the womb of its mother). and if the Nafs/self/soul/ego is not controlled well then it will be always asking for more and more.. and the spirit will be weak and prisoned. the spirit and the Nafs has inverse/opposite relation(one looking to this world and another to the afterworld).
And Allah created for all the elements of our body a desire/shahwa/appetite. the eyes like to see the beautiful views/colors and the ear like to hear the nice rhythm/words/sounds and the nose will like the nice smell and the hands like to touch soft things and the stomach like the delicious food.. and most important is the brain that its desire is in the knowledge and surely the best knowledge is the knowledge about Allah.. since the best is to know/be with the giver of gifts(provider) than to know/be with the gifts(sound brain say so). the best is that we live with our body in this world/dounya while our heart/mind is with Allah and the afterlife/akhera. by another word oppose the nafs and do not always reply its request unless it is good for the akhera/afterworld.. and whenever you lose in a battle stand up and fight back again.. as the fight will not end except with the end of our life in this world. And as the self knows the two ways; way of righteousness or wickedness.. "And (by) a Nafs/soul/self and He who proportioned it. And inspired it (with discernment of) its wickedness and its righteousness. He has succeeded who purifies it. And has failed who instills it(with corruption)"(91:7-10)
Another meaning, the good points are like the light and the sins are like the darkness and the good points erase the bad ones.. so always monitor your heart and see if it is carrying a light by intending/want/will to do good deeds for its return to Allah in the afterworld) or is it carrying darkness of the sins of this world. The good points or light are found in every small/big good deeds.. and the bad points or darkness are found in every small/big sin.. so whenever our heart is in the state of darkness we should remember Allah and return with our good intention willing to please Allah.(intention is very important and its place is the heart.. and if it was sound/good then all our deeds are good/sound. Knowing that we are not angels who have only brains(that knows that its benefit is in the relation with the giver/provider of gifts and not in the gifts given) without ego like us, that is why they do not disobey Allah's orders. and thanks to Allah that He is forgiver whenever we say sorry please forgive us. it is His character nobody force it on Him, He like to forgive and pardon. Elhamdoulellah that Allah is our Lord.
May Allah bring to our Nafs its taqwa(consciousness with Allah) and may Allah purify it for us, He is the best to purify it. Al Salaamou alaikum