The best mortification I find is that of being persecuted by others on account of Christian qualities in your character. Everywhere I go I am insulted in one way or another for the faith, and it, like Padre Pio says it should do, "hurts".
However, not willing to change my religion for that of hopeless paganism, and persevering in what I have begun since my conversion, I endure daily. Not a single day passes without me being ridiculed for my belief. Not one single day. Just 5 mins ago I got it through a phone call. This is the fruit of the intercession of the saints like one St James the Apostle who called us to practice wisdom in meekness. If the world tramples on us, that is a grace, because just men are tried in the furnace of humiliation.
Other than this I envy the OP who wishes to do penance. Once I am finished my training I think to obtain a quiet home in which to pray and suffer all day, and to cut off the world. I have no desire at all to work 9-5 or to have this "duty of state" that others speak of. I know that when I go before my judge that he will esteem my 9-5 job as worthless, but he will place merit on the things I have done in the hope of pardon.
I cannot at this stage have a conversation about mortification, but I can about suffering, but it will not be long before I undertake what you undertake now as penance. God chooses His victims because He finds them acceptable. Remember soulguard in your prayers I implore thee.