Do remember that the broken edges can be sharpened and your hands can be injured while doing the repair. Therefore this is highly recommended that you should use gloves in the process of repairing.
Secondly, there is a limit to the repair of the broken cup. In case your cup is broken into many small pieces it cannot be repaired. In this case, it is best to leave the cup like this and put it in the dustbin. It cannot be repaired. If you want you can shed some tears on it but this will be of no use and you have to move on with your life.
Finally, if you have a cup that is microwave-safe or dishwasher-safe and is broken. There are high chance that the cup may not be able to exhibit the same traits which it used to be in the past.