Use of the word design in this post means "evolved". I am used to conversation that uses design. When we talk about nature I mean evolution.

It occurred to me that instincts do not work for favourable results (good for life stuff). Instincts are designed to help reduce the effort that body/mind has to put in doing something or designed to be favourable for the human body and mind.

This is bit tricky. Based on our genetic make up, we are comfortable with certain ideas and reality. So our instincts drive us to maintain this comfortable situation. Direct implication of this is that strategies driven by instincts may not be beneficial for the social context or the problem at hand. Because instincts maximize comfort and what is comfortable for us may not be beneficial for us.

We hear people say "go out of your way", "go out of comfort zone", you will be able achieve more.

An example to make thoughts concrete:
People try to avoid their friends when they have to explain some uncomfortable issue. But that might create misunderstanding. I am sure you can think of more.