You either a blessing or lesson

At first you where a blessing
the best thing that ever happened to me
My everything but is it possible that a blessing could turn in to a lessing?

...Well I learned that it is...

Why did you break my heart
Why did I even let you in to my mind
When i let you in you told the depression to come over

You told the depression to bring the weed so I can ruin my lungs
Why did I let you in
Why did I trust you
Why was I nice enough to let you use my body...
Why was I so stupid?