Direct Answer: A texting boundary is an agreement you make with yourself about how much energy you invest in your phone. It involves accepting that your partner's reply speed is 'Their Choice' (governed by their busy schedule or mental bandwidth), and committing to put your phone down ('My Choice') rather than double-texting to self-soothe.
Modern texting creates an artificial illusion of constant presence. When a partner doesn't reply instantly, your brain treats the delay as physical abandonment. The urge to text again, call, or accuse them of ignoring you is an involuntary attempt to force a reassurance. However, this controlling behavior usually triggers a defensive withdrawal from them, creating the exact distance you feared.
If the message is genuinely urgent (e.g., logistical emergency), call instead. If they routinely read and ignore important time-sensitive messages, that is a pattern of behavior. Stating: 'I need to coordinate schedules by 5 PM; if I don't hear from you, I will make my own plans' is a healthy next step.
Move the app off your home screen, turn off read receipts, or use physical distance—leave the phone in another room for 1 hour while you complete a specific real-world task.