get easier with time.
how do you judge how loud you’re singing?
if you can hear only yourself and nobody else, then reduce your volume slightly.
at first, even this can be difficult if you’re not used to listening to your own voice and other voices at the same time.
a simple trick is to cup your ear with your hand. you will then be able to hear your own voice very clearly without having to increase your volume. by adjusting the angle and shape of the ‘cup’ you can adjust the mix between your own voice and the others around you.
you might focus in on your own voice to start with to make 