Nervousness and fear seem to be a practically consensual and appropriate response to smoking DMT, especially on the first occasion. I remember I was trying to hunt the stuff down for like 3 years (until I learned I could extract it myself

), asking everyone and their mothers if they knew anyone who had the remote chance of obtaining DMT. Well once I finally got my hands on some, I was like, "wait....am I really gonna do this?"
I know that occasionally on these forums you'll see an experience go awry, but in my experience of DMT, it's more forgiving, euphoric and positive-leaning than other psychedelics can be. I very rarely have a sour experience, but then again I've also established a pretty healthy relationship with it. I respect it, and conversely it feels like it respects me back.
The experience is always much shorter than expected, and even if something frightening or dysphoric does happen, it's only gonna be for a minute or two and then there's usually a sense of detachment from it whether it was the most blissful thing or most terrifying, like the kind of detachment from a dream or a nightmare (when you're in it, it can be very engaging, but afterwards it's kinda fleeting). It's a very important lesson to be learned that no matter how intense things are or how outlandish and surreal things may seem, everything will work it's way back to normal relatively quickly. You don't have to worry about putting yourself back together --- it just happens.
Two words of advice are to start low at 10-15mg dosage and slowly work your way up over time as you adjust to the lower level effects and ease your way into the higher effects. Also don't worry about attaining a "breakthrough" or being concerned with whether you've just had one or not. Something can be taken out of virtually most of the experiences if you're open and paying attention. Exercise caution, but I'd recommend taking the plunge. I've helped many with their first experiences, and there's been maybe like a 5% rate of unpleasant experiences. Take a couple of minutes to meditate before going into it, and just get ready to kick back and let it work it's magic and roll with the flow.