What should I choose, Life or Nirvana?
The problem is that the idea that if I get Nirvana I will not be reborn again seems discouraging.

This is a problem because you think that being reborn is good but actually it is suffering. If you want to be reborn in a heavenly realm you should know that these realms are also impermanent and it is much harder to practice the dharma there. And you also have no idea how much you might have suffered in samsara.

In SN 15.3, the Buddha said this.


  "Long have you (repeatedly) experienced the death of a mother. The tears you have shed over the death of a mother while transmigrating &amp; wandering this long, long time — crying &amp; weeping from being joined with what is displeasing, being separated from what is pleasing — are greater than the water in the four great oceans.
  
  "Long have you (repeatedly) experienced the death of a father... the death of a brother... the death of a sister... the death of a son... the death of a daughter... loss with regard to relatives... loss with regard to wealth... loss with regard to disease. The tears you have shed over loss with regard to disease while transmigrating &amp; wandering this long, long time — crying &amp; weeping from being joined with what is displeasing, being separated from what is pleasing — are greater than the water in the four great oceans.
  
  "Why is that? From an inconstruable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating &amp; wandering on. Long have you thus experienced stress, experienced pain, experienced loss, swelling the cemeteries — enough to become disenchanted with all fabricated things, enough to become dispassionate, enough to be released."


If you want to achieve nibanna then practice the noble eight fold path. 


  "Of those, right view is the forerunner. And how is right view the forerunner? In one of right view, right resolve comes into being. In one of right resolve, right speech comes into being. In one of right speech, right action... In one of right action, right livelihood... In one of right livelihood, right effort... In one of right effort, right mindfulness... In one of right mindfulness, right concentration... In one of right concentration, right knowledge... In one of right knowledge, right release comes into being. [4] Thus the learner is endowed with eight factors, and the arahant with ten.


You must also practice the four frames of reference. I’m not going to say how to practice it here but these four frames of reference are not four different exercises. Right mindfulness comes before right concentration so I think you should practice it if you want to achieve nibanna.