Can you provide more details, like how much you smoked, from what tree did the spice come from, how it was extracted, etc?
It should be a joyful experience, of course there is fear, but that is normal when you are taken well outside of your equilibrium. I have not had a scary, fearful DMT experience yet, nothing but profound beauty, and amazing sights and sounds...
You say you 'Know you want this, but you need to be neutral, expect nothing, and you will be shown a world beyond your wildest imaginings..
Just let go, tell yourself there is nothing to fear, you'll always be here, and you will return. The spice is trying and wanting to show you something, so let it take hold of your senses, your embarking on something which is so very old, and something truly so very special.
Step up to it like i did the other day, try 20mg, then 25-30mg, then if you feel like going again, step up to the mid 40'smg range, you will then know what to expect, for when it eventually takes you to a door, the gateway, with all that visual splendour put aside, you will be ready, and instead of fear, open your mind and body and just let go....