Yes you are both spot on. 5 grams . What the fuck was i thinking. It's kind of funny because for the last three weeks or so i was only ordering 2 grams at a time as a way of cutting down my consumption,had a week off the shit,then go and order 5 grams. Total insanity. Engaged debit card before brain. Lesson learnt. Must go to bed.
You were thinking - I've done deadly over the last week so time to treat myself and since my body has had a break, that means I can do a shitload this time. Subconciously of course

Fuck it, don't beat yourself up too much about it. Do remember it and learn a lesson from it. I've had some fucked up mad sessions on meph and the "comedown" I had after was not from low brain chemicals, low energy, whatever - it was from the shame that I'd allowed myself to go so out of control.
As the guys above say, buy small quantities. After my last binge I was planning to stay away from it for a few weeks or a month or so. But then came along a great night out where meph would have suited perfectly so I ended up buying a 1/2g. Actually only did a 1/4g that night, went home when everyone else was going back to a party, felt 100 times better about myself the next day.