Longing can make the past look simpler than it was. You may miss someone's humour, familiar routines or the future you imagined while also knowing that parts of the relationship hurt you.
Missing is not a decision
Feelings often reflect attachment and memory, not a complete evaluation of whether returning would be right for you. They can show up even when you have made a considered choice.
Keep the whole picture
If it helps, write down both what you miss and what led you to leave. This is not a case against the other person; it is a way to remember your own experience when nostalgia becomes selective.
Take time before acting
A wave of loneliness does not require an immediate message. Give yourself space to settle, talk with someone you trust and consider what would need to change for contact to feel healthy and safe.