Gretna's Horwood puts hand up for Celtic winner
He said: "I stayed in and I cost the side the game. I apologised to the players for that but I couldn't have done anything, I was tired because I had worked my socks off.
"I saved one off the line but I cost us the game.
"We stuck to the game plan and we did well, it was the last five minutes that killed us."
Gretna boss Davie Irons could hardly believe that his side had lost the game.
He said: "To say I am disappointed is an understatement.
"I thought we had something from the game.
"The boys were magnificent and their effort and commitment was clear for everyone to see.
"They had not caused us too many problems although we had our backs to the wall.
"It's just hard to take losing at such a late stage of the game."