Love, and do what you like! Saint Augustine
"If you like wrong things, you will soon find the quality of your love affected..."
( Letter January 16, 1908, Underhill p. 113)
One theme that Underhill provides in her writings is the theme of "Affections", and this is not uncommon for the mystics. She understood that thinking and acting are often guided by one's affections, so when she equates "wrong things" with one's love, she is talking about the quality of one's affections. This particular theme can be found in her classic book, "Mysticism: The Purification of Self", she speaks about three phases of the mystic, in particular "the lover". In short, the lover, for Underhill represented the human need to be loved and to love and if one seeks right affections, then, all those who seek God must set their affections upon Him. The lover is the stage where one becomes aware of misplaced affections and bringing them in harmony with the one true affection of our lives, loving God and loving others.
"It seems to me that your immediate job must be to make this love active & operative right through your life..."
I wouldn't ever say that this is all that easy and we certainly cannot move toward perfection, a life without wrongdoing, but the focus of our lives don't have to be sin oriented. The centrality of one's faith must be in setting one's affections toward seeing things in a "real" light by "loving everything for and in God". I would like to make one point about this though, Underhill certainly does not mean by any of this to be a self help kind of religiousity...
"...So with sins--as we advance, our conscience gets more delicate, & acts of self-help which once seemed almost
laudable, now look hideous."
In other words, there must be a basis for one being able to set their affections upon God in the first place. The fact that human beings act in wrong ways is never the debate, what is argued is how one can and must deal with this. Underhill has made the assumption that her friend Robinson had already pursued and started a relationship with Jesus and from that foundation she could focus on love in Christ and would result would be a life free from a life guided by wrongdoing. The problem that Robinson had was that although she submitted her life to God, she didn't know how to deal with depravity she struggled with daily.
A couple of answers emerge from this letter: 1) develop a rule of life, 2) view the dark night struggle as a time of growth and 3) spend time meditating specifically on the Scripture specific to Jesus. Without getting into all three of these too deeply, I think it would be safe to say that all three, although not required, can point one's affections toward the object of true love itself, Jesus! It's a start, it's a discipline and ultimately it is a matter of faith fueled by real love.
"Of course it is deplorable that we should all hesitate to make temporal sacrifices for eternal gains" ---Thomas å Kempis