Trees and wires. Oh my!
I did line clearance tree trimming for 18 years with lots of storm damage overtime.
Wires! When they're hot they'll kill you, when under tension they'll rip your head off.
The damnedest thing about both forces is you can not see either one. There is no way of telling, just by looking at a wire, if it is hot or under tension.
Another thing is wires can disappear in the back light / shadows of trees, limbs and foliage. Blend right in. Be extra observant here.
Either way, dealing with wires just takes some basic common sense, intuition, and a reasonable understanding of general physics. And that last part we go to school everyday to learn. You better believe it.
Supplemental reading, vids and mentors can sped ones' understanding, and significantly lessen the hard knocks of learning solely on your own.