Amina Inloes, Amina Inloes is originally from the US and has a PhD in Islamic Studies from the University of Exeter on Shi'a hadith. She is the program leader for the MA Islamic Studies program at the... Answered 1 year ago

By making us in pairs, the Qur'an is saying that we are pair-able, not that we are specifically created for one other person. 

Some people marry many times, some marry none, the Prophet had quite a few wives, so it isn't appropriate to say there is a single pair that is written.

Predestination and free will is a blurry area. Perhaps sometimes marriage is predestined and sometimes it isn't.

In any case, it is wrong to say that it is wholly written because there is at least the appearance of free will when we choose to marry someone or not to marry someone.

Sometimes the argument that marriage is predestined is used to justify other wrongs such as cultural taboos on marriage or wrong reasons for rejecting someone.

Also, our understanding of destiny is that there are two types of destiny, things that are absolutely fixed and things that are changeable. So even if we are destined to marry someone, we don't know for sure whether this is fixed or changeable. Allah, as the all-powerful, has the option to change destiny in any way. Prayer is said to change destiny. 

Plus it is always good manners to pray to Allah and acknowledge Allah as the source of all things.

So it is always good to pray!