Texting isn't a lesser form of communication, it's just a different one, with its own rules. Most of the friction in text communication between partners comes from applying the assumptions of spoken conversation (tone is obvious, timing doesn't matter, brevity is fine) to a medium where none of those things are actually true.
Say the tone, don't assume it's obvious
"Can we talk later" reads completely differently depending on what's added to it. Alone, it can sound ominous. With a little more context, "can we talk later, nothing's wrong, just want to catch up," it reads as exactly what it is. When a message could be read multiple ways, it's worth spending the extra sentence to make the tone explicit rather than assuming it's clear from context you can see but your partner can't.
Match the medium to the message
Logistics, quick check-ins, and affectionate messages all work well over text. Anything with real emotional weight, a grievance, an apology that matters, a serious conversation, generally works better with more bandwidth: a call, or in person. A useful rule of thumb: if you're not sure whether something will be read the way you mean it, that's usually a sign it deserves more than text.
Don't make your partner guess from silence
A delayed reply during an emotionally loaded exchange often gets filled in with the worst interpretation available. If you genuinely can't respond properly right away, even a short "saw this, can't talk properly right now, will call you in an hour" prevents your partner from spending that hour assuming the worst.
Read your own message like a stranger would
Before sending anything with emotional content, it helps to reread it as if you'd received it cold, with no knowledge of your own intended tone. Does it read as neutral as you mean it, or does it come across sharper without the tone of voice you'd have used if you'd said it out loud? This single habit catches a surprising number of messages that would have landed wrong.
Know when to just call
If a text conversation has gone back and forth more than a few times without actually resolving anything, that's usually a sign it needs a different format, not more messages. "This is getting complicated over text, can I call you" is a completely reasonable thing to send, and it usually shortens a conversation that would otherwise have dragged on for another hour.
Good texting between partners isn't about writing perfectly worded messages. It's about noticing when the format itself is working against what you're trying to say, and being willing to switch to something with more room for the tone you actually mean.