Several decades ago, in the field of medicine, it was discovered that the body can avoid certain illnesses if a person is vaccinated i.e. inoculated with a radically weakened strain of those diseases. Through this process, the body produces antibodies custom-made weapons to guard against the illness.

The principles of healing the body, according to Maimonides, apply equally to remedies of the soul.1This can provide us with a positive way of viewing minor difficulties in the execution of an important project. A weak dose of opposition early on in a venture can serve as a “vaccine” against more severe and difficult adversity later on.

Igros Kodesh of the Rebbe, Vol. 11, p. 58