Question Summary:
How do we know that failure was because of laziness or Taqdeer?

Question Detail:

How can we determine that behind our failure in a specific task whether our laziness is culpable or Allah's will is responsible?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
We are living in the world of means. [Asbaab]. We are required to adopt means to fulfil our needs. If one sits back and does not adopt means, then the failure is definitely attributed to one’s negligence. When one adopts means, he should not trust in his means, as the means are not effective in themselves. Our belief is Allah is muassire haqeeqi [the real causer of effects]. To place ones trust in ones means is against our belief. Once a person adopts all the necessary means in achieving anything, he should place his trust in Allah and Taqdeer. Whatever happens after that, whether ones objective is fulfilled or not, it is the decision of Allah. If ones objective is not fulfilled, he will still be rewarded for adopting means and submitting to Allah and Taqdeer. The greatest act of worship is to submit to Taqdeer and be happy with the decree of Allah. If this attitude is entrenched in an individual, he will have no grief and regrets for anything.
And Allah Ta’āla Knows Best
Ridwaan Ibn Khalid Esmail [Kasak] 
Student Darul Iftaa
Katete, Zambia

Checked and Approved by,
Mufti Ebrahim Desai.