The Mercy is already there, with our selfish du’as we want to change that … the purpose of du’a is not fulfilment of it … but to be drawing closer to Allah (SWT). Sometimes du’as are not accepted because Allah (SWT) wants the slave to continue asking - placing him at the doorstep of Mercy.
It is my belief that Allah (SWT) has already given us what is in our best interest, but we don’t realise it, so we do know what is in our best interest - it is our taqdeer. Our weakness causes us to ask for something different, the Mercy in this is that our displeasure with our kismet causing us to ask from Allah (SWT) in du’a is equal to a reward … so this is how the Mercy should be understood.
Again the way the marriage is being viewed and the guy is being viewed and the predicament is being viewed is in the sense that “they are evil” … however, the way to view all of these things is that after getting in the marriage or predicament has it made the person remember Allah (SWT) more or less? If more then that has been a good thing despite them feel stressed over it and if less then it is a bad thing despite them being happy over it.