给出一个段落，要求在其中找出并替换其中所有的代词为具体的指代词。
"John was exhausted after a day of work. He headed home, but had to stop at the store to pick up groceries. When he was done, he realized he forgot his wallet in his office. He was frustrated, but decided to go back and get it."
"John was exhausted after a day of work. John headed home, but had to stop at the store to pick up his groceries. When John was done, John realized John forgot John's wallet in John's office. John was frustrated, but John decided to go back and get John's wallet."