Dedicate your external to the eternal internal, not the ephemeral internal
When authors write books, they often dedicate their book to some person – that person may not be much mentioned in the book itself, but the intent of the book is to glorify or please that person. Thus, dedication of the book signifies the intent of the book, even when that intent is not immediately apparent from the content of the book.
Whenever we work in the external world, we are inspired, motivated, energized by some inner conception – we may work because of our desire for money or power or prestige or pleasure or whatever else. Our work is thus dedicated to that inner conception.
Most of us dedicate our external to an internal that is ephemeral, that is short-lived. The material world itself is temporary as are all the things in the world. In this light, when we dedicate our external to some ephemeral internal, we set ourselves up for frustration and even devastation when that ephemeral thing either goes away or its capacity to give us pleasure goes away. How can the internal go away? What goes away is the external and we are left with the internal craving that is unsatisfied and frustrated – and that makes us similarly dissatisfied and deluded.
The Bhagavad-gita (12.10) urges us to dedicate our work to Krishna, to work for his sake, and assures that by such work, we can attain perfection. The Gita (12.08-12) outlines various levels at which we can practice bhakti. The preceding two verses talk primarily about the internals: about being mentally and intellectually absorbed in Krishna (12.08) and if that is not possible then striving to focus on him (12.09). This verse acknowledges the reality that while living in this world, we have to function here, and such functioning needn’t be rejected as mundane. It can be spiritualized by a devotional intent, even if in content it seems largely mundane or even materialistic. The Gita itself demonstrates the spiritualizing power of intent when it asks Arjuna to fight for a divine cause, thus conveying that even an activity that might seem blatantly anti-spiritual such as fighting can be spiritualized by a devotional intent.
Of course, we need to practice regular sadhana to cultivate and nourish this devotional intent. But the inclusiveness of bhakti means that we march towards Krishna even while doing our mundane-seeming work because even that becomes dedicated to Krishna, thereby making our entire existence dedicated to him.