So this next chapter is jumping ahead in time a bit. I'll go cover Minerva and Severus' meeting with Albus a little later, but for now this is Severus time to be alone and think. Unfortunately I'm not J.K. Rowling just a girl with too much time and love for these characters.
I saw this poem on my favorite blog, and it reminded me of how Severus might be feeling after Lily had died..
"All I ever wanted you to do was feel this feeling. Be this way. Exhale the sky.
All you ever did was feel different. Be away. Wash your hands with air.
All I love is a feeling. I still feel this way. I cannot breathe.
I still forget there's air out there.
I still forget how white hot everything was.
I still forget myself.
There's nothing wrong with this.
There's nothing true about this.
There's nothing.
You were once everything I felt.
You were once everything.
You were, once.
And if love moves like air, then teach me how to dig my nails into the palm of my hand so I can remember what you once felt like." ~I Wrote This For You

Minerva excused herself from the Headmaster's office. Severus also excused himself from the office and started making his way to the Astronomy Tower. Once at the top he was able to take his cloak off and let himself feel the cold air prickling his skin. After everything he had gone through that day it was nice to have a little time alone.
He kept on feeling like this was all some sort of dream, or maybe this was truly the afterlife? Everything seemed to be going the way he wanted, so there was no way this was real.
There was still this gnawing feeling in the pit of his stomach that presented itself when he first lost Lily.
Now she was back and wanted to be with him.
Him?
It all seemed so surreal, being given a second chance at life with the woman he loved. Literally.
Just as he was allowing himself to smell the pine trees of the forest, feel the cold wind on his face and stop thinking just for a moment he felt someone small snaking their arms around his torso. Turning around to be greeted by the most beautiful witch he had ever seen, wearing a smile that lit up her green eyes. Wearing the smile just for him.
"How did lunch go?"
"It was really great, we got a nice chance to try and be normal. We were able to watch him while we were gone but it's different to actually speak to him in person, watch him speaking to me. Very weird"
"I can only imagine, I know that it's been difficult just talking to you and we don't share blood"
"Thank god for that, Sev"
She then rose up on her toes and kissed him lightly on the lips, he then deepened the kiss by leaning down and grabbing her by the waist and slowly lifting her up off the ground and she wrapped her arms around his neck.
It was passionate, spine tingling, romantic, sweet, yet new. It was everything that he could have ever wanted it to be.
Slowly placing her back on the ground and releasing himself from her sweet lips he found himself staring deeply into her eyes. Perhaps searching for the answers to the questions he was asking himself just a moment ago.
"I find this all to be very confusing, let I feel like I'm feeling for the first time since I found you in Goddric's Hollow"
"It'll get easier with time, Sev. I'm not dead anymore, very much alive"
She then took his hand gently, placed a kiss on his palm and placed his hand over her beating heart.
"See?"
He was stunned by what he felt, not for the heartbeat trying to escape her chest, but for the placement of his hand.
"I've loved you from the moment that I met you, I'm sure I was blind before I met you Lily. I will love you always. For the rest of my life, whichever one this is. You mean everything to me."
"Sev.." Not sure what to say, for never being as gifted with words as he was she decided to show him something that could show that she too, loved him always.
She led them back to the Headmaster's office, holding his hand. It gave him great pleasure, feeling as if holding her hand inside these castle walls was one of the only things he had ever truly wanted.
Once entering the office, she summoned the Pensive and placed a memory inside. She then asked him to join her..

They were in an abandoned classroom, it looked like it had not been used for years. All the desks were pushed up against the walls. After a moment Dumbledore, James and Lily all walked into the unused classroom. Dumbledore motioned to an old mirror in the corner that Severus recognized as his least favorite mirror in existence, the Mirror of Erised. Lily and James looked barely old enough to be out of Hogwarts and after listening to their conversation, he realized that Dumbledore had asked them to the castle to officially join the Order of the Phoenix. After accepting straight away, Lily began to look around the classroom and found the mirror to be very interesting.
"Professor, what is this beautiful mirror doing in this dusty classroom?"
"Ah Lily, that is the Mirror of Erised. It shows us our heart's deepest desires. It is being moved shortly but I am allowing it to stay in the castle for a little while. Go ahead and take a look.
Lily then moved toward the mirror, while no one else in the room could see what she saw but the real Severus and Lily viewing this memory. She approached with caution, almost aware she may not like what she sees.
She positioned herself in front of the mirror and took a sharp intake of breath as she saw herself look to the left and instead of seeing James she saw Severus.
Erised Severus walked up to Memory-Lily, took her in his strong arms and kissed her passionately. They seemed lost in each others eyes and she noticed that his sleeves were rolled up, no Dark Mark.
She looked happy and healthy, he looked clean and they both looked truly in love.
A look that she never saw herself giving James.
"What do you see Lil?" James, her fiance, the man she came with and the man she would be leaving with asked her.
"Oh, um, I see us together, getting married. I also see two children, a boy and a girl. They look like us. They're standing behind our legs and you're giving them hugs and kisses"
"Wonderful Lils!"
"Well I think it's best if you two are off now, this mirror can drive the best of us to doing bad things"
Before exiting the room Lily turned once more to look at the mirror,
"Don't worry, Lily, your secret will always be safe with me"
Lily looked at the old wizard with shock and awe, before exiting the room she gave a numb nod of her head and the memory dissolved.

As Lily and Severus came up from the Pensive she noticed him crying, openly.
"I'm so sorry Lily, I could never deserve you"
"Sev, stop that right now! You've paid the price for your actions, you saved my son from danger for years. Even risked your own life well after I was gone."
Severus grabbed her by the waist, looked deeply into her eyes and said,
"I will never disappoint you again, Lily. I will make it my life's mission to make you happy, to care for you, every day for the rest of my life if you'll let me stand by your side"
"I wouldn't have it any other way, my Half Blood Prince"