From an anxiety-management perspective, why does ending bad relationships matter? Because when who you're pretending to be and who you really are aren't the same, anxiety pops up to ruin the party.
Several years ago, before I became more serious about pursuing my spiritual growth, aside from my long-time friends, many of my relationships were focused on partying. These relationships were with type A entrepreneurs who "worked hard and played hard." When they went out, they stayed out all night, drank lots, and didn't think twice about doing drugs. They were good people, sure, but the relationships were phony.
They were based on status, indulgence, and short-term highs. Over time, I realized that these relationships were preventing me from becoming the person I knew that I was put on earth to be. I put parameters on relationships with people who led me astray. Other relationships I straight-up ended. This was key to my personal evolution. Now, when I run into friends from my old days, we say hi and I'm happy to see them, but our lifestyles don't mesh. I'm closer to being the version of myself that I want to be.
I salvaged a few relationships from my party days, with people who I really care about, but instead of joining them on their party path at night, I ask them to join mine by having breakfast or lunch together.
Maybe right now you're thinking, "What about bad relationships that I can't end, and not because I lack the courage?" That's a great question. We all have people in our lives who are chosen not by us but for us and who we must relate with. Most often, these are family members, and it might not be possible, reasonable, or ethical to cut them from our lives.