I find it generally hard to get going as the stealth A, but I finally manage to pick up some shields early. By the time I'm in sector 7 I have a Burst Laser MK 3 and a Heavy Laser MK 2 to go with my dual laser. I also have a full crew with two Zoltans that I hired from one store. Things are looking pretty good.
Halfway through sector seven I hit a node where I need to go through an environmental hazard to proceed. No big deal, I can backtrack to get around it. I have to fight two rebel fleet battles as I backtrack though.
I manage to reach the jump point to the next node, and I'm like "Hell ya!"
However I see that there are two nebula I can go explore, and I figure it is worth one more rebel fleet battle to do so. I explore them no problem.
However now there is a store in the top right. Exploring it would be one more fleet battle (total 2) on my way back to the jump point, but what the hell. I don't really need anything to beat the boss and I only want the achievement for getting to sector 8 anyway, but the temptation of maybe picking up a preigniter or something is strong.
Turns out the store was a bust, so I head back to one of the two nebula I just cleared (which I have to fight the enemy fleet at now because I dawdled).
It turns out what I didn't notice was that the same nebula I had previously visited turned into a Plasma Storm while I was at the store. WTF? I didn't even know that was possible. Achievement lost

I went on to kill the boss, but it was a very hollow victory.