Material sense gratification, sinful activity kills the propensity to serve Krishna.
Hammer every thought in your mind thinking of how to serve Krishna.
Every living being is anxious for full freedom because that is his transcendental nature. And this freedom is obtained only through the transcendental service of the Lord.
Srimad Bhagavatam 1.6.37,
A devotee should always aspire to live in the association of advanced devotees and engage in the service of the Lord through the parampara system.
As a kshatriya has no problems while taking the wounds on his chest. similarly a devotee has no problems taking wounds while serving Krishna.
Determination means to serve Krishna inspite of bodily inconveniences.