Have you ever stolen someone else's design?

its really sorry to say there was one time i really did that! that time i must make a design work and i found another one pic that is not mine on a resource site,that was really good for my design so i used it and just changed a little in my illustrator!
everybody thought that was my original idea but i always worried what if someone else found the truth one day? and also i feel really shame to do that! i wont do that stupid thing again!