There is a special kind of tuning with the इष्ट according to your nature and behavior.
We in Sanatan chose our इष्ट very specifically.
He/she whenever chosen for worship is chosen mostly in सौम्य form, the reason being easy to please and love rather than fearing.
Let’s for example take अंजनेय as इष्ट. There are two स्वरूप famous of Hanuman दास भाव and वीर भाव.
Hanuman is mostly worshipped in his दास भाव as then we say praises of श्री राम and Hanuman gets easily pleased as राम नाम is everything for him.
If in any ways you are praying Hanuman and the moment he is to appear you remember his वीर भाव and he appears in such I guarantee you, however big साधक you be you will get frightened.
Just by the mere sight of वीर हनुमान you will be frightened enough to death if you are not अधिकारी of that.
That is why it is important to chose the form to worship specially.
Let’s imagine you worship जगतमाता in her सौम्य स्वरूप as गौरी! She is the most beautiful, most divine, as serene beauty even without ornaments just with काजल in her eyes she is superior to any beauty in this universe.
She will take care of you, take you in her lap and give you all you can wish as she is the mother, जगन्नमाता!
Even you can worship her as काली. She is सौम्य too till you treat her well.
(There are other ways to worship her too crating relation as father, brother but don’t try I say).
काली is उग्र form of माँ but is still accessible easily if you are a true seeker.
But let’s suppose you get उग्र while the साधना and रणचंडी comes.
Will you be able to please her?
She is hard to please even my महादेव himself. Who are you to do so?
Even Shiva in form of गौरांग is very subtle to please. He is भोलेनाथ!
Why won’t he be pleased? Actually he gets pleased even by subtle praises.
But beware if you try it with महाकाल! He is different. The ultimate रुद्र! You see him and there is no coming back. No one can remain alive after seeing महाकाल.
There is a reason I say it is so difficult to die with भगवत् name on your lips. You think it is easy?
You will very very rarely see a true साधक or योगी doing this.
Your कर्म just doesn’t allow you to do so.
If you die with भगवत् name you reach his abode, become one with him.
हर (har) is a name of शिव. Why?
Because he takes away!
महाकाल is the eternal.
If you die with हर on your lips you meet into him.
It is not easy I tell you.