"I can do hard things!"
What do you have to do that is difficult? Cleaning your room? Doing a big assignment for school? Lifting weights at the gym? Guess what - you can do it! Things that are hard are difficult, but they give you great gains. Your room gets clean. You make an "A" in Math. You get stronger and faster.
When we work hard to get through things we are persevering. We have to develop grit and use our strength to help us achieve great things.
You can accomplish things that are hard!