Heaven structures mortal life, somewhat like graduation structures medical school

When I argue that the essence of Christianity is Jesus's gift of post-mortal resurrected eternal life in Heaven; come people have said that this devalues, renders pointless, and stops us from working hard at, this earthly mortal life.

Insofar as there is an ethic from mainstream secular-materialism; it is that we modern people are better, more moral, than those in the past because instead of daydreaming about an imaginary Heaven, we instead focus on real and present issues such as our personal happiness and development; helping other people; and making this world a better place.  

But I believe the opposite is the case; and I will illustrate this with an analogy of the possibilities of the relationship between medical school, and medical practice as a qualified doctor (also discussed here). 

Analogy

This mortal life on earth = being a student at medical school

Resurrected eternal life in heaven = working as a doctor

If we take the secular materialist view that there is only this mortal life; then this is analogous to being a medical student but never qualifying, never practicing as a doctor - indeed a closer analogy is that there are only medical schools, only student, only the processes of training - but there is no such thing as working as a doctor. 

Once the novelty of medical school had worn off, the endless drudge of attending lectures, learning material, studying for and doing examinations - analogous to the business of doing chores, and maintaining ourselves alive as mortals - would soon being to seem a futile treadmill if the process was not going anywhere! 

Yet this is how mainstream modernity depicts mortal life on earth; when it assumes that death is annihilation. Mortal life is then a difficult and tiring process, leading - nowhere.  

When medical school is structured by the aim of qualifying and working as a doctor; this does not devalue medical school, but instead the intent of qualification is exactly what gives the process purpose and meaning. 

The prospect of eternal life in Heaven serves to structure this mortal life analogously to the way that qualification as a doctor structures the student training at medical school.  

Properly considered; Heaven does not devalue mortal life; but is exactly what gives mortal life purpose and meaning. 

Further: If you found yourself in medical school but had no knowledge of (indeed denied the reality of) being-a-doctor; then your life as a medical student would be meaningless - it just wouldn't make sense. 

When the structure of medical school is designed to make students into doctors, and that is why students are required to do unpleasant things like dissect corpses, learn biochemistry, practice interviewing patients, and get interrogated by senior medics etc. 

If it wasn't for the intent of preparing the student for working as a doctor - such activities would be experienced as gratuitous intrusions into the necessities of daily living, and lifestyle choices of undergraduate pastimes - rambling conversations, sports, college societies, personal relationships etc.  

But when the reality of "doctors" is lost or rejected as a possibility - then medical school just becomes a sequence of arbitrary and pointless experiences and activities (some pleasant, others very nasty). 

And this is analogous to the mainstream modern person's experience of mortal life: life just seems like a meaningless sequence of happenings and duties - aiming nowhere, going into nothingness. 

When there is no aim or purpose, then the events of life can have no meaning. Personal experiences that might be understood in terms of opportunities for learning, or preparation for the life to come; are instead reduced to a sequence of random occurrences - whether nice or nasty.  

With nothing but annihilation at death to look forward to; the only reasonable attitude to life seems to be short-termist and focused on increasing pleasure and reducing suffering in the here-and-now.