Many people misunderstand asceticism and its relationship with mysticism. Asceticism is self-discipline. It deals with the spiritual practices that we use in order to open ourselves to the presence of God.
Mysticism is the experience of God. It’s the experience of oneness with God. This is both a gift of God and something we prepare ourselves for. But even in the spiritual disciplines we need grace.
It is not mysticism or asceticism, but rather it is both. We need to do the spiritual practices to prepare our heart, to deny ourselves, and to die to self. It is through this death to self that we move into oneness with God.
Both the spiritual disciplines and the experience of God are given by grace. It is God working in us both to do and to will for his good purpose (Phil. 2:13). We would not seek God unless God had first sought us. We love him because he first loved us (1 John 4:19).