I don't think it matters to cut one or two leaves out that are shading. If you take into account nature, plants lose leaves all the time, its just the volume of what you remove needs to mimic that in nature. I don't think going mental on the pruning is good for obvious reason, likewise, I don't think its right to go to the other extreme and remove nothing, under any circumstances. Removing something that won't be absorbing much light and therefore having much use can only help the plant opperate more efficiently. You just have to exercise good judgement and restraint, that goes for the overall thread as well.