confused about ending to Deadpool: Wade Wilsons War......(Possibly Spoilers)

This book made me think of Deadpool as a sycopathic killer, and for some reason I dont think thats necessarily what the writer was going for... I was also extremely confused by the ending, instead of explaining the whole thing the writer some how sneeks in a word of advice about life. To me it just doesnt make sense at all. Can someone please exsplain it to me?