Sefer Divrei Yisroel says that when it says that Yitzchok went to ‘pray in the field towards evening’ it means that he went to recite tefillos about the destruction of the Bais Hamikdosh and the darkness of golus.
It is stated in the Medrash (Yalkut Hoshea, Remez 522): ‘Rebbe Yochanon ben Zakai once was walking in Yerushalaim and Rebbe Yehoshua was walking behind him. They saw the ruins of the Bais Hamikdosh and Rebbe Yehoshua said, ‘Woe to us that the house, the place where our sins were atoned, was destroyed.’ Rebbe Yochanon told him, ‘My son. Do not feel bad. There is another way to receive atonement. What is that? Gemilus chasadim’.
Yitzchok went out towards evening to daven to Hashem and he cried about the destruction of the Bais Hamikdosh, where Klal Yisroel received atonement for their sins. He worried how we would receive atonement after being sent into exile. He then lifted his eyes and saw ‘gamalim’, camels, coming towards him. This can be understood to mean that he saw gemilus chasadim and understood that it can bring about atonement just like korbanos. This led him to be calmed.