Advice is an interesting thing to give because by it is opinionated in nature. It is influenced more by the previous experience of the giver, more than it is by the taker. Because advice we give is usually one of many possible courses of action, there will always be doubt in the recommendation. The only way of really knowing what advice to take, only becomes evident after it has been taken.
Where doubt is an omnipresent reality, the best advice we can give is definitive advice. Advice which is acted upon quickly and fervently. When advice increases self belief in the receiver, it is often more valuable than the advice itself.