This reminds me quite of my own childhood.
Not simply because of the titling, but because of the overall simplicity of the composition. Let me tell you of my childhood to better get my point across.
I was born in a crime-infested city, but we soon left that life for one in a quiet yet uneasy trailer park.
I had memories of where we began as a family, from the quick yet strong bonds I had with the children I used to live with amongst the trailer-homes that accumulated into a single trailer park. We had actually planted an oak tree in the small plot of land we had, and for the short time I was there, I had friends, and I was happy. But it was no life for a family if we wanted more from life.
So, we built a house from a 5 acre plot in the outskirts of the town. We sold the trailer, but the tree remained, even today in the same place. Nobody lives in that plot when I had last seen it.
I was around 6 when I first began to live in our new home. It was a new beginning, but a very lonely one. Although we had a few homes close to us, there were probably 4-5 homes where we lived when we first moved in. I had no friends, and at that time I was quite the avid reader, so I spent my elementary school years playing my RPG's and the like on my SNES along with the occasional novel.
Even today, my mom still says they were just games, but they were in essence the foundation from which I find the source to my passions.
From loneliness in a quiet and creative environment, sprouted despair but yet also spawned love and passion. From this, I created the world I wanted myself to live in, along with a character I feel helped to represent who I was on the inside.
He was sad, but he was also very strong, (I was having extremely horrific nightmares at the time, not normal for a kid that age. Blood and entrails on the walls, screaming corspes hanging from the cielings, yeah...not pretty) and I began to feel his presence in my dreams, and from that point on I began to fight against my fears and weaknesses.
One night, I(still) vividly remember a dream I had when I was walking with a silver haired boy with a white outfit, and when we stopped walking at the end of the path, I found myself beside him, and after I shook the silver haired boy's hand, he drifted into the sky like dust and the dream ended. To me, that was the turning point of my life in my childhood.
I'm thankful for everyone I've met in my life, but most of all I'm thankful that I was able to meet my imaginary friend. To me, I felt that the Imaginary friend was a reflection of who I was (and still am).
He still hasn't left me, and I'm happy that I was able to grow up with him. To me, his company was greater than that of a friend's. (To only friends I had either had themselves seen by me when they were alone, or used me as a emotional punching bag. I still remember coming home with bruises all over my body.)
Even though my as well as my family's may have been imperfect, I feel that we had the best life we could have led, and I'm happy that I had a true friend, an imaginary one.
tl;dr
My imaginary friend was and is important to who I was, is, and will be.