Answer
Both assets and liabilities can be engaged in devotional service.
For example, suppose you fall sick. That is the unfavorable side of your karma. Even that can be utilized to increase your Kṛṣṇa consciousness. You have to find ways and means to engage it in service.
If you are sick, you may have to take leave from work for a few days. Since you are already confined to bed, you can use that time to hear Śrīla Prabhupāda's lectures, read his books, increase your japa, and deepen your remembrance of Kṛṣṇa.
In this way, even an apparently negative circumstance can become spiritually beneficial.
Similarly, suppose you are burdened with debt or someone is constantly troubling you. The problem may continue for some time. Whether Kṛṣṇa solves it immediately, gradually, or allows it to remain longer is ultimately His decision.
But in the meantime, your mind can learn greater dependence on Kṛṣṇa. Such situations can intensify your prayer, your chanting, and your surrender. Thus, even difficulties can be converted into opportunities for spiritual growth.
The same principle applies to favorable circumstances.
When difficulties come, we increase our dependence on Kṛṣṇa. When favorable circumstances come, we increase our gratitude.
Instead of thinking, "I deserve this," we think, "Kṛṣṇa, thank You. I do not deserve this mercy. Thank You for Your kindness."
In this way, gratitude becomes our response to good fortune.
Many devotional qualities develop only when we are placed in different situations. If everything always went perfectly, we might become proud and gradually forget our dependence on Kṛṣṇa.
Therefore, both happiness and distress can help us advance spiritually.
The real art is learning how to connect ourselves emotionally with Kṛṣṇa in both sukha and duḥkha—in favorable and unfavorable circumstances. When we learn to do that, both the assets and liabilities of our karma become valuable in devotional service.