What is a blessing?

 I think that Rabbi Dr. Abraham Twerski Z"L makes a grave mistake in his interpretation of the verses of Parshat Vayehi (Twerski on Chumash, 2003); it is a mistake that others before him have made, and others will make as well. 

Criticism is not a blessing. Even if it's constructive - and even if it's meant to help. 

It is an interpretation that's almost become normative, that Yaakov Avinu blessed Reuven for example by spotlighting his impetuosity, or that the former heaped on Shimon and Levi by cursing their wrath. 

That is not what the verses share, nor is it what they intended. 

Rather, these are the exact words at the encore, at Yaakov's final moments: 

All these are the tribes of Israel - twelve - and this is what their father spoke to them and he blessed them; he blessed each according to his appropriate blessing. 

Thus, sage advice is not a blessing; it is certainly not a curse, but when you tell a person how he or she can improve it is a kindness of the greatest proportion, but it is clearly, as the Torah delineates - different than the act of a blessing a human being. And thus, the dichotomy in the text. He spoke to them, and then he blessed them. When you have something on your chest, especially when nearing the end, it's imperative to convey it to the other party, and then your heart is clear to bless, to caress, to pray for the other's wellbeing, the height of any blessing. 

But not as Rabbi Twerski writes: "Jacob knew his children. He instructed them to each fulfill his unique potential, maximizing the particular talents, skills and character strengths with which he was created. This is the greatest blessing of all."

If Jacob, Yaakov Avinu had not imparted an actual blessing on Reuven for example, or Shimon and Levi, how could they have gone on with life knowing that their father's parting words were of scathing rebuke?