Hi there DMT-Newbie. You really aren't alone in having fear, anxiety or anticipation about smoking spice. I think most of the folk on the Nexus get pre-flight jitters - I know I do, often to the point that I manage to procrastinate from smoking for months on end. I made some changa in the New Year that I have only just summoned up the courage to smoke! Then again, I've yet to break through, so for me the sense of anticipation and fear of the unknown is strong.
It's strange, because often after taking DMT I have less anxiety. I think if I leave it too long between sessions, the fear builds up too much and I find it a challenge to smoke again. As someone who has no previous psychedelic experience, I would advise starting with low doses - 10mg should be fine. DMT is a weird experience (but often very pleasant), even at such low doses. Let your mind become accustomed to the DMT sensation before upping the dose. I myself am very cautious , which is probably why I haven't broken through yet!
Get yourself a good, accurate scale!! I also recommend abstaining from caffeine on trip days, as it might make any anxiety insurmountable and you'll lose your bottle (courage). Meditation is a very good skill to learn also, as it teaches you to let go of any tension.