The key to sanctification is unity with God…holiness, oneness with God.
God may allow suffering to occur in our lives for many reasons. There’s enough suffering that occurs naturally that we should learn how to “convert” that suffering into prayer, offerings to God, without setting out to suffer.
Smile more, take the stairs with a smile and an offering, tackle assignments with more vigor, work a bit longer, be a bit more cheerful than you want to; when you get ill, don’t let everyone know it. Develop a spirit of sacrifice, a sporting spirit about things.
When faced with suffering…convert it - with God’s grace into a prayer or an offering to God or for others.
If we tend to put our comfort in between us and God…then the Church - under the direction of a spiritual director, may recommend little fasts or other little sacrifices in order to detach from one’s love of comfort.
But I think most people would recommend using the material that God gives us throughout the day as means to grow in holiness, and ever more constant prayer with God, our Father.