Please understand that you haven't thrown it all away at all!!! You ask if there's still hope. There is certainly hope. Actually, there's even more hope now than ever before!! Let me explain why. The Gemoroh says "Habah letaher misaayen lo - he who comes to be purified will be helped" and also "Biderech she'adom rotzeh leilech molichin osoh - in the way a man wants to go, they help him" Why do Chaza"l speak in plural form: "misayen lo - they help him" and "molichin oso - they lead him". Shouldn't it just say that Hashem helps him? So the Maharsha and the Kedushas Levi explain that every resolution and every effort a person makes, creates a Malach (an angel). And when the army of malachim gets large enough, it has the power to help the person overcome all the obstacles and lead him to where he wants to get.
So all times you held back and desired to be holy over the past period you were clean, has created tens and hundreds of Malachim that will help you now to stay clean for much longer! That's why there's even MORE hope now than before.
Yes, it hurts to fall (I know the feeling very well) but the nachas ruach that we give Hashem when we ignore the fall and get right back up, is the greatest there can be!
Use the fall to learn from. Learn to always keep your guard up, etc... And then the fall itself will become a zechus and turn you in to a Tzadik!
Though you are starting again from "day 1", don't think for a second that your past accomplishments are down the drain! Quite the contrary: Every Hisgabrus you have over the lousy Yetzer Hara is yours forever! Even if you fall again after that Hisgabrus.
The Steipler writes that one who was Misgaber over the Yetzer Hara of Hashchosas Zera L'Vatalah, even if he goes on to fail and fail, time and time again, it is that initial Hisgabrus which will guarantee him an ultimate triumph in this matter over the Yetzer Hara, no matter how long it takes.
I can attest to this personally. I tried and tried so many things so many times. I had already basically given up on myself and resigned myself to the fact that I will live my life as a sinner. Yet, now that I look back and I marvel at being clean for 10 months (B'Chasdei Hashem) there is no doubt in my mind that that initial Hisgabrus I had for a very short time a very long time ago is what propelled me to finally win my battle many years later.
Keep strong. Don't listen to the Yetzer Hara's stupid logic. You are winning the battle and will ultimately win the war!