Desire what you control
Principle 14 from the Enchiridion
Bring desire back to your own choices and conduct. The more your peace depends on an outcome, the more power that outcome has over you.
Original Passage
If you wish your children, and your wife, and your friends to live for ever, you are stupid; for you wish to be in control of things which you cannot, you wish for things that belong to others to be your own. So likewise, if you wish your servant to be without fault, you are a fool; for you wish vice not to be vice, but something else. But, if you wish to have your desires undisappointed, this is in your own control. Exercise, therefore, what is in your control. He is the master of every other person who is able to confer or remove whatever that person wishes either to have or to avoid. Whoever, then, would be free, let him wish nothing, let him decline nothing, which depends on others else he must necessarily be a slave.
Modern Interpretation
Epictetus puts it bluntly: if your peace depends on an outcome you cannot control, that outcome controls you.
It is not a reason to stop loving people. It is a reason to stop asking life for guarantees it cannot give, such as another person always being there or always acting as you hope.
You may still care deeply while bringing your attention back to your own choices and character. Other people are not possessions, and no relationship comes with a guaranteed outcome.
In Practice
You keep checking a partner's messages and reading every change of tone as a bad sign. Without realizing it, you are trying to guarantee something you cannot fully manage.
Return to your part: communicate honestly, set the boundaries you need, and treat the other person with respect. You still do not know how everything will turn out, but uncertainty no longer gets to choose your behavior.
Reflection Question
What outcome are you holding so tightly that your mood now depends on it?