If you attempt certain things at the right time, they are easy to accomplish - in fact, they almost get done by themselves. If you undertake them before the time is right, not only will they fail, but they will often become impossible to accomplish even when the time would have been right.
Other quotes by Francesco Guicciardini
Be careful how you do one man a pleasure which must needs occasion equal displeasure in another. For he who is thus slighted will not forget, but will think the offence to himself the greater in that another profits by it; while he who receives the pleasure will either not remember it, or will consider the favour done him less than it really was.
Like other men, I have sought honours and preferment, and often have obtained them beyond my wishes or hopes. Yet never have I found in them that content which I had figured beforehand in my mind. A strong reason, if we well consider it, why we should disencumber ourselves of vain desires.
Conspiracies, since they cannot be engaged in without the fellowship of others, are for that reason most perilous; for as most men are either fools or knaves, we run excessive risk in making such folk our companions.