Going onto another tangent...
The RAW is a bit more nuanced. It lowers your Parma and your form resistance. There's been ample debate that individuals without Parma can't voluntarily lower their resistance, which is important for friendly creatures of might and apprentices.
It also means casting a spell upon yourself with a lowered Parma requires a bit more concentration than a lot of magi can muster: a Very Hard Sta+Concentration ability roll of casting another spell while maintaining another. So, while magi can cast touch range spells on themselves, it's actually not easy, or it shouldn't be based on the RAW. We can imagine that an average magus will have a Sta +Concentration of around 6 (Sta 2, Concentration 3, spells specialty), it means that about ~8 times in 10 the concentration roll will fail, which means the spell fails. Since most spell failures cause fatigue, I'd probably put fatigue on the magus in this case, too.