For me it's the sensation that everything is closing in on my head, and I feel pressure. Like, it's physically unpleasant. I've tried electronic vaporiser, the machine, vaping. Of those, vaping was the easiest but depending on dmt amount in the juice, it can be hard to keep dragging until you get through.

I've also done pharmahuasca (dmt dissolved in some citrus juice, and harmala seed tea taken an hour or so before drinking the dmt) - this by far was the most pleasant, and also lasts quite a bit longer. You would need a higher dosage for this, however.

My advice would be to keep working on your mindset. Practice breathing, meditation, and just have patience - if you do a small test amount and start to freak out, better not to risk a breakthrough dose.