The Prophet (saw) had a camel named Al Adbaa and he (saw) would race people and beat them. Once a Bedouin came and he had a young camel below the age of 6 years old and he beat the Prophet (saw) in a race. The Sahaaba were affected by this. The Prophet (saw) said it is Allah’s Law that everything which rises in the dunya, Allah will bring it down. (Bukhari)
We learn from this:
When you reach your peak, you’re going to go downhill, physically or otherwise.
He (saw) mentioned that anything of the dunya will go down. He didn’t say aakhirah! So anything done for the aakhirah will not go down rather it will go up. For example, a project or anything left as a legacy!
When something is done for Allah with sincerity, knowledge and emaan, it will increase.