The point of meditation is to still the mind, 'no thoughts,no thinking', and then you can catch stray thoughts and emotions as they arise, watch them, and let them go; it is, taking control of the monkey mind.
One of the easiest ways of coming to one pointed mindfulness is to visualize following the path of a square:
breathe in - four beats up the left edge - hold four beats along the top edge - breathe out 4 beats down the right edge - hold four beats along the bottom edge. Four or five times should be enough to quieten the mind then a simple mantra like - no thoughts, no thinking - can be used to make awareness of stray thoughts easier.
One pointed mindfulness is as true for Christian devotional meditation as it is for Buddhist meditation, and probably all other forms, you cannot concentrate on one thing if the monkey mind is in charge.