Self-denial is the sacrifice of one's own desires or interests, and can take the form of asceticism or abstinence. In the context of Buddhism, self-denial can also be understood as no-self or anattā.
Meditation is a practice of training the mind or self-inducing a mode of consciousness in order to realize a benefit. It requires discipline and the ability to concentrate and focus. Self-denial can help develop this concentration by eliminating the desires that lead to wavering thoughts.