The phenomenon you're experiencing is complex, but I have some helpful advice:
First, focus on your mindset and environment--find a comfortable, clean, and private space, ideally alone.
Practice daily meditation to sharpen your mind, which can better prepare you for the experience of elevation through earthly or medicinal substances.
When reintroducing cannabis, use meditation to navigate any troubling thoughts that arise (Just be present with all cognitive patterns). Remember: You are NOT your thoughts!
It's challenging, but accepting your dualistic nature is key to gaining a greater perspective of your psyche.
Practice! Practice! Practice!
Lastly, be mindful of your physical state--avoid getting high when sleep-deprived or dehydrated.
Namaste.