Diego and Luna loved to play fetch in the park every day. Luna was the fastest dog in the neighborhood, and Diego couldn't help but laugh as she chased after the ball, her tail wagging with joy.

One sunny afternoon, Diego and Luna went on an adventure to explore the woods. Luna bounded through the trees while Diego followed, the sunlight streaming through the leaves above.

As the days went on, Luna started to slow down. She began to sleep more and play less. Diego could see that she was feeling tired and weak, so he made a cozy bed for her in their favorite spot at home.

Diego spent every moment by Luna's side, telling her stories and singing her favorite songs. He gently stroked her fur, whispering words of love and comfort as Luna's warm eyes looked up at him.

One starry night, Luna gently closed her eyes for the last time. Diego held her close, tears streaming down his face. He knew she was at peace now, running and playing in doggie heaven.

Though Luna was no longer with him, Diego knew that she would always live on in his heart. He smiled through his tears, remembering all the wonderful times they had shared together.

From then on, whenever Diego felt sad, he would look up at the sky and whisper, 'Goodnight, Luna. I love you.' And in his heart, he knew Luna was looking down, wagging her tail with love.