Engineers use "conventional" electron flow, in which we say the current flows from the Positive side of a power source to the negative side. The arrows on all component schematics, such as diodes, follow Conventional flow because, well, engineers designed and made them. So with a diode, using conventional flow, you say the current flows the same way as the arrow on the diode... makes it really simple.
HOWEVER, current, or electrons, ACTUALLY in real life flow from the negative side of a power source to the positive side. For some reason, this is what they usually teach technitions and hobbists pick up on it. Becuase of this, they have to think backwords, in other words... they have to think the current flows AGAINST the arrow of the diode in a schematic. Even though it's the real way it happens, it can get confusing...
i suggest you use Conventional flow, more textbooks that i've seen use it, and it makes reading schematics alot easier.