In China's traditional culture, "spring" is often regarded as a new beginning, and it is the season when everything recovers and is full of vitality. The old friends here can be understood as old friends and familiar people, and can also be understood as the state of past lives or past lives. Therefore, "seeing an old friend in spring" can be understood as that although a new beginning has arrived, the expected person or thing has not appeared. This may mean full of expectation for a new beginning, but some nostalgia for the old state or people in the past.
This sentence can also be interpreted as a mixture of expectation for the future and nostalgia for the past, regret for not getting what you want and desire for a new life.