At least the athletes will always have the accomplishment, the records, the ring. Their bodies and skills may erode but the things they did remain in the record. Same for actors and musicians, they lay down a performance and either it was recorded or articles and memories of it remain behind them.
The ones I feel for are the beautiful women who are employed in TV and film mostly for their looks. For every Meryl Streep there are thousands of lovely women who don't make the grade and hundreds more who get cast but simply are not very good at the craft. They age, their bodies are no longer so fresh, and suddenly what little career they had is over. Some few of them pick up enough acting chops to hang around, but most are so much disposable meat and get treated as such.
Then they're in their 40's and 50's, looking back on that beer commercial or failed TV pilot that was their high water mark.