Answer
Nama, mantra japa, bhajana, kirtana, etc. are also means of spiritual practice, but they are not the sole means.
In a previous post, I had clarified that nama japa should be practiced in such a way that it becomes an automated habit. Whether you consciously wish to or not, the nama japa should continue on its own. Some people use their days off to cultivate this habit — they spend the entire day doing nama japa sitting in solitude, so that the Name ascends onto their tongue, enters the mind, and then continues silently as manasa japa. So no matter how early you leave for work, the nama japa will keep running on its own.
The second point is that Bhagavad Dharma is a dharma based on the Gita. And the greatest distinction of the Gita is that it gives supreme importance to Karma Yoga. In Karma Yoga, whatever work you do, you do it as an offering to Ishvara — you renounce attachment, you do it for Ishvara's pleasure, and you regard it as service to Ishvara. So when you do this, however early you leave for the office, going to the office itself becomes service to Ishvara; the work at the office too is dedicated to Ishvara and performed as His service. This in itself becomes a profound spiritual sadhana. So where is the need for self-reproach?
As I mentioned earlier, even at the office, during lunch break, do make it a point to read the Gita for 15 to 30 minutes. That would be an excellent use of the lunch hour at the office.
Gradually, when all your office duties are performed for Ishvara, dedicated to Ishvara, carried out with purity and sincerity, they will transform into divine service. Then indeed, sadhana itself becomes the means!