My second time on MDMA was on a 160mg pill, and I was extremely floored and disassociated for 10 minutes or so. It wasn't a bad experience- just one I was not ready for. I would go for half, but if you eat the whole thing- you'll survive, just be prepared. My experience was also a pill that had a higher dose of ketamine than you'd find in pressed MDMA pills, so that may have been a factor.
Preventing a rough come-up is difficult if you're prone to it on MDMA, many people experience a "psychedelic panic" in the come-up. You can eliminate the lengthy come-up that is associated with swallowing a pill by changing your method of administration to bumping, which is quicker. If the idea of that sounds like too much work or unpleasant, there are tolls you can use just to calm yourself down and work through it. Talk to friends, sit down, and try to remember that it will all feel great soon.