Premanand Maharaj Ji
What exactly is dhyan, and why can't I do it?
Dhyan needs a pure heart and sadhana
Dhyan is complete focus on your goal, such as the Name or God's form. First the heart must be pure and the mind one-pointed, and sadhana (spiritual practice) is needed for it.
Becoming fully focused on the goal is dhyan. Whatever our goal is, the Name or the Form, we become absorbed in God's divine form.