The pressures of his career left him very little time for his family. He felt he was doing an injustice to them. He did not give them enough time. His conscience was pricking. He felt guilty. The guilt was because he felt he did not do justice to his duty. The consequence was guilt. It's a natural consequence.
There are 3 sources of guilt :
If you are follower of a religion, then the priest will be the cause of your guilt when you violate the scripture. If you go against the norms and beliefs of 1 person, a few people, or society in general, then they will make sure you feel guilty. They will tell you, you are morally wrong. The last source of guilt is your own self, this can also be called as "karmic" guilt. Let's assume you insulted someone, then you will suddenly feel uneasy, guilty. This guilt comes straight from nature. It's not externally induced, but infact it manifests itself in your internal restless, guilty feeling. You can choose to ignore the external sources of guilt coming from the scriptures, and society. But the guilt of self is real. You will feel it's pain without mistake.
The guilt of self arises when you violate your own value system, where hypocrisy becomes your clothing. You know you are not transparent, not honest. You have double standards. You are not fair. And most importantly, you do not interact with the humanity around you with sensitivity. Human values are missing. You suddenly feel really unwell. You go to a spiritual doctor for help. This doctor does not give the answer. Instead, he asks you, "how are you feeling ?". And your reply is, "I feel guilty".