John Owen on Temptation & Watchfulness

Watch the Heart
That part of watchfulness against temptation which we have considered
regards the outward means, occasions, and advantages of temptation; we
now proceed to that which respects the heart itself, which is wrought upon
and entangled by temptation. Watching or keeping of the heart, which above
all keepings we are obliged unto, comes within the compass of this duty also;
for the right performance whereof take these ensuing directions:
Let him that would not enter into temptations labor to know his own
heart, to be acquainted with his own spirit, his natural frame and temper, his
lusts and corruptions, his natural, sinful, or spiritual weaknesses, that, finding
where his weakness lies, he may be careful to keep at a distance from all
occasions of sin.

.....
Again: as men have peculiar natural tempers, which, according as they
are attended or managed, prove a great fomes (diseased material) of sin, or advantage to the
exercise of grace, so men may have peculiar lusts or corruptions, which, either
by their natural constitution or education, and other prejudices, have got deep
rooting and strength in them. This, also, is to be found out by him who would
not enter into temptation. Unless he know it, unless his eyes be always on it,
unless he observes its actings, motions, advantages, it will continually be
entangling and ensnaring of him. This, then, is our sixth direction in this kind:

Labor to know your own frame and temper;
what spirit you are of;
what associates in your heart Satan has;
where corruption is strong,
where grace is weak;
what stronghold lust has in your natural constitution,
and the like.

taken from around page 200 in Kapic & Taylor version of OWEN