In case of fiancés I think the emphasis is on guiding yourselves together using the “Song of Love” from Saint Paul together with a good analyses of passions and emotions. Moral law can help of course.
I wouldn’t consider “discernment (of the Spirits)” -Ignatian Spirituality- to be paramount because the concept integrates too many factors and realistically the future spouses might be better served with a simpler and practical approach at how they manage communication and feelings both individually and together (searching simple internet articles on communicating with your partner can yield better ideas and results.)
If anything the fruits of the Holy Spirit (Charity, Peace, Joy) are the indicators to pursuit, marriage is also about yielding and not letting suffering we may encounter overshadow love.