Been there so many times before my union. My guess is that most people who make it went through those thoughts at least once.
Separation sickness. It shows up as lethargy, low energy, and even physical pain when your counterpart isn’t around. The emotional turmoil shows up physically too, that’s not in your head. Wanting to quit doesn’t mean you’re failing or weak. The constant pursuit is energetically draining. The effort to reconnect can cause actual exhaustion. You’re dealing with high highs and low lows while also processing your twin’s emotions alongside your own.
Take a break from trying to force things if you feel like you need to. This isn’t a race. I don’t think there’s anything wrong with questioning whether you can keep going. It’s part of it, unfortunately.