This question is most easily addressed through an analogy, described in this excerpt from Shinzen’s publication, What is Mindfulness?

Think of mindfulness as attentional fitness training.
 

When you do fitness training, you practice formal procedures (exercises) that alter the fabric of your body in two ways:

• They increase your baseline strength.

• They increase your baseline flexibility.

When you do Mindfulness training, you practice formal procedures (meditations) that alter the fabric of your consciousness in two ways:

• They increase your baseline sensory clarity.

• They increase your baseline equanimity.

The goal of fitness training is not to achieve a temporary state of strength and flexibility that is present when you do the exercises and then vanishes during the rest of the day. The goal is to gradually increase your baseline of strength and flexibility.

In other words, the purpose of fitness training is not to create certain temporary states in your body, but rather to develop certain abiding traits in your body.

The situation with mindfulness training is similar.

The goal of mindfulness training is not to achieve a temporary state of clarity and equanimity that is present when you meditate and then vanishes during the rest of the day. The goal of mindfulness training is to gradually increase your baseline of clarity and equanimity throughout the day.

In other words, the purpose of mindfulness training is not to create certain temporary states in consciousness, but rather to develop certain abiding traits in consciousness.
 

In order to increase your baseline of physical strength and flexibility, what would you need to do? You would need to learn how to properly perform the exercises. You would need to do the exercises with regularity. And you would need to maintain your exercise program over time.

The same is true with Mindfulness training. You have to learn how to do the formal procedures properly and practice them with regularity and maintain that practice program over time (months, years, and, hopefully, decades).

By practicing with regularity, I mean do at least a few half-hour sessions per week plus a mini retreat every month or so. Alternatively, you could do a couple of longer retreats every year coupled with your weekly self-practice sessions.