A couple of thing I wanna clarify:
1> This is for Potter fans only, specifically those who have read the Deathly Hallows - waise baaki junta bhi padh sakti hai - u'll understand the sequences.
2> I have written this as, according to my imagination, Snape would have written in his personal diary, that is, if he ever kept one.
Before he told Lily that she was a witch:
I love her. She is the most beautiful creature I have ever seen. And, she is a witch, although she doesn't know it yet. I have seen her perform magic. We will be going to Hogwarts together. I know Hogwarts will be much better than home. I hope they allow me to stay there during the holidays also. She doesn't know me - I am not sure whether she has even seen me yet, but soon she will know me. I will tell her that she is a witch and that she will be joining Hogwarts,just like me and I'll tell her everything that I know about Hogwarts. Maybe then, she'll like me.
On the day he tells Lily that she is a witch:
It couldn't have been worse. I told her that she was a witch but she didn't believe me. She and that Muggle sister of hers, looked at me as if I was some animal escaped from the zoo. I had been planning of this day for a long time but somehow everything went wrong, as it usually does in my life.She will realize that I was right when the letters from Hogwarts arrive. Then she'll know that I was speaking the truth all along. Maybe then, she'll like me.
On the day before leaving for Hogwarts:
She is angry with me again, and all because of that stupid Muggle sister of hers. Who told her to come sneaking around when I was talking to Lily? These stupid Muggles don't have brains. How was I supposed to react when she made fun of my clothes? I didn't mean to harm her but my anger burst forth and a twig fell on her head from the tree. And now Lily blames me for it and isn't talking to me anymore. However, soon we will be going to Hogwarts and everything will be fine again. I sincerely hope she is in Slytherine because that's where I am going. She MUST be in Slytherine.
Sometime during the 4th year:
That bastard James is showing too much attention towards Lily and maybe Lily likes him too, although she says that she despises him whenever I ask her. I can't hate anyone more than I hate him. Other than that, I am very happy with my life. I have made good friends. This Lord Voldemort seems to be getting powerful everyday - and he needs followers. I find the prospect of joining his ranks very attractive. From early childhood I have learnt that power is everything and we wizards should use our powers to take over the world from the Muggles. Why should we, the more powerful people, live hidden from the Muggles while they are free to do whatever they like? My friends share my feelings,although Lily doesn't understand me. She has lived a secluded and safe life till now,how can she be anything other than philosophical about good and bad. But I am practical and I am sure I'll be able to convince her that my path isn't wrong.
After he calls Lily Mudblood:
What have I done!! I shouldn't be allowed to live. I called Lily "Mudblood". And all because of that Potter and his despicable friends. It was so humiliating - hanging upside-down in mid-air, controlled by Potter. I was blinded by anger and I lost control of my mind. How could I have called her, the person I love, such a foul name!! What will I do now? I went to her later and asked for her forgiveness but I already knew that I had committed an unpardonable offence and any amount of pleading couldn't bring me in her good books again. She doesn't like my friends and nor the path I have chosen in my life. Seems the love of my life is lost forever.
After Lily's death:
HE KILLED HER !! The Dark Lord killed Lily !! My Lily DEAD...why am I still alive? After all I did to save her, I was unable to do so. I have no reason to live now. Even though she married Potter and I had no chance of getting her, I lived with the hope that maybe some day she will be mine, but now even that hope is gone. I have nothing left in life.I did all that I could. I had pleaded with the Dark Lord to spare her life. I told him that I don't care if Potter and his child die but please don't hurt Lily. I had even contacted Dumbledore, at great risk of the Dark Lord's getting to know this. I had told him of the Dark Lord's plans of visiting Godric's Hollow. I had asked him to somehow save Lily's life. I told him that I will do anything in return of his saving Lily's life - even though it means saving Potter and his child too but even the greatest wizard in the world wasn't able to save Lily from the Dark Lord. And my Lily is dead now. But how did the child survive? And what happened to the Dark Lord? Dumbledore says that his power is broken for now but soon he will return to full power - not that I am going to help him anymore, after he killed my Lily. But whenever he returns I will do my best to make sure that he is gone forever. I can't let the killer of Lily live on. Dumbledore says that my aim in life now should be to protect Potter's son. How can I care for the son of that bastard? But then, he is Lily's son too and she died protecting him. I can't let Lily die for a vain cause. Moreover, Dumbledore says that the child has Lily's eyes. I wish I could see them now. But she is gone forever, never to return. And I am left with this onerous burden of protecting the child she died protecting.
Sometime during Harry's first 5 years:
That Potter is just like his father. No regard for rules, insolent, hot-tempered. He seems to hate me as much as I hated his father. I hate him too but still I'll protect his life with mine if it comes to that. All this just because of you, Lily.
After Dumbledore tells him that Harry must die:
Potter Must Die!! Not that I have any kind of affection for him. All this while Dumbledore made me believe that he and I were protecting Potter for Lily's sake. But now I know that Dumbledore was raising him so that he could use him against the Dark Lord. Dumbledore never had any intention of letting Potter live. He just used me to protect Potter until protection was no longer required. I spied for him. I have put my life in danger every single day for the last 2 years just to keep Potter safe and now Dumbledore tells me that Potter must die. Still I'll follow Dumbledore's instructions because they will lead to the fall of the Dark Lord and I can't rest until I punish Lily's killer. Dumbledore himself will die soon, at my hands. I will have to commit this crime to save Draco's soul from damage - as Dumbledore put it. I have a long list of tasks ahead of me that Dumbledore has entrusted me with, will I be able to complete them successfully? Or will my life, that has been a failure till now, end in failure too?
The last entry:
The battle for Hogwarts has started. All that is left for me to do now is to somehow get to Potter and make him listen to everything I have to say. But this is the most difficult task. How will I find him amidst the chaos of the battle? And how will I, whom he considers to be his biggest enemy next only to the Dark Lord, make him believe me? Dumbledore, your instructions demand too much of me. But I will carry them out even if it costs me my life.
