How do I mortify the flesh?

(Thomas Watson, "The Christian Soldier" 1669)

The flesh is a bosom traitor; it is like the Trojan horse
within the walls, which does all the mischief. The flesh
is a sly enemy—it kills by embracing. The embraces of
the flesh are like the ivy embracing the oak; which sucks
out the strength of it for its own leaves and berries. So the
flesh by its soft embraces, sucks out of the heart all good.

The pampering of the flesh, is the quenching of God's Spirit.
The flesh chokes and stifles holy motions—the flesh sides with
Satan. There is a party within us, which will not pray, which will
not believe. The flesh inclines us more to believe a temptation
than a promise. The flesh is so near to us, its counsels are more
attractive. There is no chain of adamant which binds so tightly
—as the chain of lust.

In the best of saints, do what they can, sin will fasten its
roots in them, and spring out sometimes with inordinate
desires. There is always something which needs mortifying.
"Put to death, therefore, whatever belongs to your earthly
nature: sexual immorality, impurity, lust, evil desires and
greed, which is idolatry." Colossians 3:5.

How do I mortify the flesh?

1. Withdraw the fuel that may make lust burn. Avoid
all temptations. Take heed of that which nourishes sin.
Those who pray that they may not be led into temptation
—must not lead themselves into temptation.

2. Fight against fleshly lusts with spiritual weapons
—faith and prayer. The best way to combat with sin is—upon
our knees. Beg strength from Christ. Samson's strength lay in
his hair; our strength lies in our head—Christ. This is a mystery
to the major part of the world—who gratify the flesh rather
than mortify it.