Question Summary:
Question about kufr and shirk.

Question Detail:

 
I am perpetually fearful of committing Shirk or Kufr. I tend to over-analyze each and every statement I utter or think and connect it with Shirk or Kufr somehow. I am so paranoid that I continuously re-state the Shahadah. Lately, this fear has increased because I am about to be married iA and acts of Shirk and Kufr annul one's Nikkah. It is obviously not easy to re-do the Nikkah again and again should one commit Shirk/Kufr continuously. Could you provide me with a detailed explanation of what constitutes Shirk and Kuffar. I recognize that most of the thoughts that I have are waswasa but the matter of Shirk/Kufr is so delicate since it takes one out of the fold of Islam that I am unable to lay off these thoughts. 
Could you also specifically answer the following queries in your reply:
There are many statements that people say commonly in a particular context, for instance people frequently refer to another as their 'dearest' or 'most beloved' or spouses may call each other their 'one and only'. Is this an act of Shirk Fil Muhabbah. Of course the intention is not that the person is more beloved than Allah SWT. 
Secondly, if you say/think something mindlessly and realize it might have been shirk and immediately repent, in that case, for instance if a person is married, would it be pertinent to redo the Nikkah. 
 
Thank you

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
 
Dear brother in Islam,
It is important to understand that this world is a test from Allah Ta’aalaa. Our primary purpose of life should be to attain Allah Ta’aalaa’s pleasure. As with every test in life, there are obstacles that we must overcome in order to be successful. One of those many obstacles is Shaytaan, our sworn enemy. Shaytaan has many webs that he tries to entangle us in. One of those is the web of waswasah. One becomes so engrossed and obsessed with a particular matter that it gnaws at his conscious every second of his life, thus steering him away from the true purpose of life.
You request for a detailed explanation of what constitutes kufr and shirk. This will not help your waswasah problem. In fact, it will infuriate it as every time you utter a sentence, Shaytaan will make your mind go through the entire explanation and see of your sentence fits within the definition of kufr or shirk. It often may be the case that you will debate with yourself as to whether or not it is kufr. Thereafter, you will start getting worried about the validity of your marriage and so on and so forth. This will ruin your life and will heavily effect your marriage life.
As for the statements mentioned in the query, they do not constitute kufr. They are merely an expression of affection for one’s loved ones.
We advise you to dispel off and ignore all such thoughts. Pay them no heed. Take no notice of them at all. Also, seek professional aid. Ideally, a Muslim psychologist will understand the matter much better and be able to assist you much more efficiently.
 
And Allah Ta’āla Knows Best
Muhammad Haris Siddiqui
Student Darul Iftaa
Melbourne, Australia 
Checked and Approved by,
Mufti Ebrahim Desai.