The donkey and the lion

I couldn’t figure out the rebus on this postcard, because I thought it was a horse, not a donkey, aka ass. I was distracted by the smoking, the snorting, and the eyelashes! So it says,

“Even though you make my ass good and tired, I have decided to drop you a line”

The person that bought this card must have been tired indeed, it was never mailed.

I was going to mail it myself, but I can’t think of anyone that makes my ass good and tired.