2 For We intend to speak of the riches stored up in this Church which Christ purchased with His own Blood, and whose members glory in a thorn-crowned Head. The fact that they thus glory is a striking proof that the greatest joy and exaltation are born only of suffering, and hence that we should rejoice if we partake of the sufferings of Christ, that when His glory shall be revealed we may also be glad with exceeding joy.
Source: Mystici Corporis Christi (Vatican.va)