Have you relook MN 19 and combine MN 125 to your understanding.
You might see how:
Indeed MN 19 is not so linear. It is back and forth to make clear the overlap steps.
1. Actively removing/preventing 3 bad thoughts to manifest & generate/maintain 3 good thoughts to enter/maintain 1st jhana.
2. Then after successful with 1st jhana, Actively stilling of vitakka vicara of 3 good thoughts to enter/maintain 2nd jhana. Because maintaining vitakka vicara is tiring the body/mind in the long run.
Then the MN 125 support it.
Now the samadhi part of N8FP include samma vayama (effort), samma sati (introspection to within) and samma samadhi (balance).MN 125 wrote:…
Then the Realized One guides them further: ‘Come, mendicant, dwell seeing an aspect of the body as the body, but don’t think thoughts connected with sensual pleasures. Dwell seeing an aspect of feelings … citta … dhamma, but don’t think thoughts connected with sensual pleasures.’
As the thinking and pondering are stilled, they enter and remain in the second jhana … third jhana … fourth jhana.
If one is successful in development of Samadhi part of N8FP, it is possible to maintain it for 24/7. Which should support your Jhana is life.