For me, I think my poly thinking was part of me dealing with jealousy and insecurity. So as I became more open to the idea of poly, I felt I could let go of some of those feelings. No longer was dating a competitive sport where the "best man wins" or whatever. Instead, people were together because they enjoyed being together. No one else can take that away.
Later, poly got me to start thinking about compersion. It took awhile of thinking about it (years) before I finally was able to internalize it. So I think poly has gradually helped me change my view of relationships and how I feel about them.