Who said "I have to try harder. Tomorrow I'll really try."?

This quote is attributed to Charlie Brown.

I have to try harder. Tomorrow I'll really try. - Charlie Brown

"I have to try harder. Tomorrow I'll really try."

Charlie Brown Perseverance

"Good grief!"

"I got a rock."

"Rats! I did it again."

"Why is it that everything I do turns into a disaster?"

"Perseverance is the key to success."

"Don't give up on what you believe in."

"I've been through worse."

"You learn to live with the pain."