How did monarchs justify and maintain their power?

Just becoming a recognized monarch meant that the leader was very good as a military leader and a political leader.When the institution became hereditary,justifications became religious,in that the monarch was chosen and blessed by God for the position.But,the monarch then had to show that s/he was a capable commander-and-chief of the military as well as an adept politician who was able to garner the aid of important people to keep the monarchical government running.

Well nowadays I don't think they use any method to justify or mantain their power because they actually don't have any. Today's monarchs only work to "represent" countries and to mantain that "nice" tradition of having a king or a queen in a great palace with the quards and stuff. Although it's a really stupid reason to justify the fact of having a crown, that can show you how stupid is having a monarchy still in the 21st century.

However, I know that some centuries ago, monarchs that wanted to take all the decitions and to have the judicial, legislative and ejecutive power of the nation (absolute monarchs), justify this just by saying that they were god's representatives in that country; and knowing how religious people were, they just believed it, beause "why wouldn't our perfect god choose the most suitable person to govern?" And they mantained it just giving great pensions to people who had the enogh power or strength to steal the crown, the nobles. And that's also why noblity didn't have to pay taxes at all. But, at least in Europe, that started to change in 1789.