Answer
That is a very good observation.
The reason is that, for a conditioned soul, determination for service is often easier to maintain than determination for sadhana.
Why?
Because a person's previous karma and conditioned nature often provide energy and enthusiasm for active engagement.
The passionate mentality that previously drove one toward fruitive activities now becomes engaged in devotional service. In this way, that same passion is gradually purified.
After all, no one can remain inactive.
There are only two broad kinds of activity:
fruitive activity (karma), or
devotional service (bhakti).
We are always active in one of these two directions.
When a person begins rendering devotional service, much of the enthusiasm and determination comes from the momentum of his previous conditioned nature. That karmic background gives him energy to work enthusiastically for Krishna.
In one sense, that previous passionate tendency is being purified through service.
Therefore, you often see that a devotee has tremendous determination to perform practical service.
Sadhana, however, is different.
Sadhana is not simply activity—it is direct association with Krishna.
When performing ordinary activities, people naturally perceive value because they expect some visible achievement or success.
With sadhana, however, one must gradually awaken an appreciation for the value of simply sitting down and chanting:
Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare, Hare Rama, Hare Rama, Rama Rama, Hare Hare.
One has to develop a deep conviction:
"This is one of the most valuable activities of my entire life."
That appreciation does not appear immediately.
Unless we understand and appreciate the value of Krishna's association through the holy name, the determination to excel in sadhana will not naturally arise.
Otherwise, chanting may continue in a ritualistic way.
Even then, there is no loss.
Because even ritualistic chanting is still contact with Krishna.
Gradually, little by little, one begins to experience for oneself what sadhana is actually doing to one's consciousness.
As spiritual realization develops, the value of sadhana becomes increasingly evident.
In devotional life, both service and sadhana are important, but they relate to Krishna in slightly different ways.
When rendering practical service, we work and then offer the results to Krishna.
In sadhana, however, we have direct contact with Krishna through His holy name, His instructions, and remembrance of Him.
Earlier, I used to describe these as two forms of devotional service:
Indirect devotional service—working for Krishna through various services.
Direct devotional service—personally associating with Krishna through sadhana.
Both are transcendental.
Neither is material.
However, because our conditioned nature already carries momentum for external activity, enthusiasm for practical service often develops more easily.
The spontaneous attraction for direct association with Krishna through sadhana takes longer to awaken.
Therefore, initially, one's willpower for sadhana may be weaker than one's enthusiasm for service.
But this is temporary.
As one continues practicing sincerely, gradually appreciating Krishna's association, that determination naturally becomes stronger and stronger. Eventually, the devotee develops the same enthusiasm for sadhana that he has for devotional service.
