Lightest punishment while teaching students?

I am very confused. Actually, I am teaching two students. I don't like to hit students because it hurts me more than the pain I give to them. Below is the picture of my students.

I love them as my child. I am unmarried. I love every child from the days when I was a child.

As you know children are very naughty but sometime they become so careless and even ignore good things which we study them. currently, the situation is the sometimes I hit them not that painful but to make them attentive. I don't like to hit them but they don't hear me until I hit them. I don't want to hit them anymore. They are very friendly to me and love me. Even after hit, they kiss me at the end of the day.

Sometimes I ask them that search another teacher who can study you well but they tell me that we don't want another teacher. So I ask them why you don't want another teacher. In reply, they wrote me.

You teach us very well and You also love us so much

Please tell me how I can deal with this and even this helps others. Sometimes I give them a punishment to stand at the corner of the room and see toward walls but it takes much time so I don't want to waste their and my time.

I feel happy when they show love towards me. Even I give them moral lectures. I am confused about hitting.

Share your experience.