I have contemplated these things and studied these words and still find the natural leaning of my mind to be nowhere near this ideal. I'm more inclined (still) to worry, to stew, to think negative thoughts (mostly about myself, which makes me just as self-absorbed as a conceited person).
But in the learning, in the meditation, I can see some progress - a growing awareness of the need to "take captive every thought to make it obedient to Christ." (2 Corintians 2:5). When the worry crops up, if nothing else I can repeat Phil. 4:6-7, present my requests to God - with thanksgiving - and expect His peace, which is beyond my understanding. When a negative thought comes up, I can remind myself to think instead about whatever is true, noble, right, pure, lovely, admirable, excellent and praiseworthy.
Ultimately, success in this area has less to do with my "ability" to focus my mind and everything to do with the worthiness of the One on whom my mind is fixed.
"You will guard him and keep him
in perfect and constant peace
whose mind is stayed on You,
because he commits himself to You,
leans on You, and hopes confidently in You."
Isaiah 26:3 (Amplified Bible)
in perfect and constant peace
whose mind is stayed on You,
because he commits himself to You,
leans on You, and hopes confidently in You."
Isaiah 26:3 (Amplified Bible)
Think about such things...