When they say "have faith", do they mean in God or in yourself?

like belive in ma syelf?

To have faith means to believe. You can believe that you can do something or think positive about it. From a Christian standpoint, a person would pray about something and do so in faith, in other words believing that God will help you through it or teach you how to get through it with the trials you overcome. Having faith just means to believe and keep pressing forward.

Yeah, have faith in yourself and you can do anything. :)

In this context I believe your teacher meant to have faith in your own writing ability. Much of writing is just letting the ideas flow. Yes, you have to narrow it to formal structure and lucid thoughts but the first step is to get the ideas out.

Can mean either, however…..mankind falls very short of the glory of God (flawed),therefore I ‘have faith’ in God who offers all mankind, the free gift spelled out in John 3:16

Hard to say what your teacher meant without knowing the context. Still, I’m going to guess that s/he didn’t exactly mean either in yourself or in G!d, but meant rather that you should have faith in the process of writing itself, that if you stick with it and don’t let your feelings of failure scare you away from doing it, at some point you will feel it starting to work better for you.