When do we consider what is beneficial and what is corrupting, and should we always consider them in matters of Sharia law?

"Sharia rulings are the true guardian for achieving benefits and averting harms. The Sharia is built upon this principle, while observing the acquisition of the greater of two benefits and the warding off of the greater of two harms when they conflict. This is decided by those deeply rooted in knowledge and acquainted with the objectives of the Sharia. Lawful piety (wara') is abstaining from what one fears its consequences. The Sharia commands pure and preponderant benefits, and forbids pure and preponderant harms. A bad outcome may be tolerated to دفع ما هو أسوأ منها أو لتحصيل ما هو أنفع من تركها. (avert what is worse than it or to achieve what is more beneficial than abandoning it). The balancing between benefits and harms becomes intense in times of tribulations, and only exceptional scholars can undertake it. A scholar constantly considers and balances between benefits and harms. However, the determination of this generally refers back to the proofs of the Sharia, not to mere opinions and personal desires."