After Kayin killed Hevel, Hashem gave him very severe punishments. The land would no longer produce for him as it did before, and he would become a wanderer, separated from Hashem's immediate presence.
Kayin then said to Hashem that as he wandered the earth, whoever found him would kill him. Immediately afterward, Hashem told Kayin that He would protect him, and He even gave him a sign for it. What changed? Hashem had just decreed such harsh punishments upon Kayin, and now suddenly He was going to protect him?
The Ohr HaChaim HaKadosh there explains that when Kayin said whoever found him would kill him, he was recognizing that without Hashem's protection, he would not be able to survive. Kayin understood that his safety was completely dependent upon Hashem, and in the zechut of that recognition, Hashem had extra mercy upon him.
This is a very powerful idea. We're talking about Kayin immediately after he committed one of the worst aveirot of all. Furthermore, we're talking about someone who spoke directly to Hashem. Yet, after he recognized how much he needed Hashem to protect him, that recognition alone was so precious to Hashem that He showed Kayin an outpouring of mercy. How much more so if a person today, who doesn't see Hashem openly, would recognize that he needs Hashem for everything?
We have opportunities all day long to strengthen our emunah in this area. Before a person leaves his house, he could think, "Hashem, I need You to protect me every step that I take." Before he goes to work, he could say, "Hashem, I need You every step of my day for success." Before making any important decision, a person could say, "Hashem, I need You to guide me." When his children leave the house, he could say, "Hashem, only You can truly watch over them." Every time we sincerely think, "Hashem, I can't do this without You," we are implementing this beautiful fundamental in emunah.
How fortunate we are. The One who takes care of us is our loving Father Who controls everything and always does what's best for us. Sometimes different circumstances bring us to truly internalize this truth.
Rabbi Binyamin Pruzansky told a story about a man named Rav Shiya Erps, the director of Camp Kol Simcha. On one occasion, he became trapped inside a large industrial freezer. The heavy door had slammed shut, and there was no handle on the inside. Despite being very handy and physically strong, nothing he tried worked to get him out. The tools he had with him couldn't get the door open, his radio had no reception to be able to call anyone, and nobody could hear his cries for help.
After nearly an hour in the freezing cold, he finally stopped trying everything and turned to Hashem and said, "Hashem, my tools, my strength and my radio have all failed me. I understand now that without You, I have nothing. You are the only One Who can save me. Please, Tatte, open the door for me."
He then went over to the door one more time, pushed gently at it, and the heavy door swung wide open. He later reflected that he had never felt such a complete lack of control. He had been so sure that somehow his own abilities would save him. But only when he truly recognized that everything depended upon Hashem did the door finally open.
If just recognizing his need for Hashem brought protection even to Kayin at such a low point in his life, we can only imagine how precious it is when we go through our day recognizing again and again, "Hashem, I need You. I know that everything I have comes from You, and I know that only You can give me what I need."