But why Machiavelli thought it is hard to gain respect, if it's all self-evident in many everyday situations? I believe because giving respect (following behaviourial norms) and having respect (feeling that awe, knowing the quality, the capability, the achievement, the greatness, etc.) are two different things. If you want respect you have to earn it - it is a common wisdom and describes well the situation. And this is where princes fell, they couldn't earn it. There were nothing extraordinary in them, besides the ambition, and Machiavelli knew it, and he did not demand the impossible. It is not easy to earn it. Being dangerous won't make you loved, and being generous won't make your feared. Those who try applying both might not know when to use each. And it is weird that while great many ways of earning respect - one can be wise, brave, consistent, steadfast, etc. etc. - people still fall short. Can we feel respect towards people (institutions) we just met and know nothing about them beforehand? I highly doubt it. We can give, but can't have. Some want respect from every new face, beyond the humanly possible live-and-let-live norm. This expectation is quite egotistical, shortsighted, unwise, etc. These people themselves never tried to respect others, never walked a mile. Even if someone is highly respectable, the proof is on him to keep himself to his nature and gain respect again and again. If he really is, in most cases shouldn't be hard, but on every occasion it will need time. And more often than not, time can be precious, therefore reputation that precede us could turn into an important factor. But that's another story.
What would Bernd add to this? I feel I kinda left out that live-and-let-live aspect which just touched in the end for example.
Tried to dig up some cool gang sign for respect. But only this the best I could find.