As an Angel, you are bound to hold your faith to the man above. Have faith in that who you do not see. You had a hard time blindly following orders from someone you've never seen.

So, you fell, got kicked out, your subscription to heaven expired. Leaving you to fall to earth where Castiel found you, only one wing intact, a miracle as it was.

Castiel however, was busy doing his thing and following God's order leaving him to leave you with Sam and Dean Winchester, the talk of the town while you were up in the skies.

You were sat on the edge of the bed in their motel room, the brothers stood in front of you, analysing you. "So what? are we to believe you're some fallen angel that somehow kept your wing?" Dean pressed. "Lay off Dean they've had one of their wings clipped, I'm sure that's traumatic for them." Sam argued. "Okay fine. but we're not babysitting you." Dean barked as he walked to the kitchenette to grab a beer.

(BASED OFF OF @FallenxGods ON POE.AI)