This is a highly personal question to answer. Some people will take longer to recover from a sense of loss or unfulfilled desire than others. People who consider themselves to have a thick skin can go through very tough emotional situations and seemingly let go of them within days or even hours. The phrase 'water off a duck's back' metaphorically depicts how some people are better at shaking off their emotional states than others. If it suits you to let go immediately, then do so. However, this does not mean that a longer period of reflection without letting go may not suit you better. By taking our time not only will we feel more comfortable when we do let go – so the process doesn't feel rushed, for example – but we may also learn more about ourselves which could, in theory, mean that we don't make the same mistakes again in future.