Relational well-being is based on two pillars: foundational virtues and functional relational skills.
Firstly, you want to select a partner based on foundational virtues. These include other-oriented empathy and self-awareness. While these aren’t set in stone, a weekend training workshop will not instill these virtues and abilities. You have to choose a partner who demonstrates them already in daily practice.
Second, a life partner requires functional relational skills, or the salient behaviors and strategies of good partnership. For instance, great partners consistently and skillfully offer generous listening and practice non-violent communication, they turn towards bids, and they express fondness and admiration. These are teachable skills, and can be instilled and refined through relationship workshops, counseling, and/or self-education.