Pair Apple Watch again without erasing

I have accidentally unpaired my Apple Watch on my iPhone. I need to pair my watch with the same iPhone again.

(But I think the same problem can probably be faced if one gets a new iPhone with an already paired watch.)

The Apple Watch is fully working. I can open the apps, see my clock-face and so on. But in the menu bar, there is a red strikethrough iPhone icon.

If I open the Apple Watch app on my iPhone and tap on start pairing, my Apple Watch does not show the pairing image as it did first after unboxing it.

Do I need to completely erase my watch or is there somehow an option to start pairing my watch again?

According to my space usage on my iPhone (Settings > General > Usage > Manage Storage), I do have a backup on my iPhone. But this is some days ago and I do not want to lose my (activity) data – so erasing my watch is really my last choice.

To put it in a nutshell: How do I pair my iPhone with my watch again without erasing it?

I was experiencing this problem when i had my phone on my desk and I would walk away from it. When I came back I found that the watch would refuse to re-pair with my phone again.

I found a quick way to force the watch to re-pair with my phone:

• Flick up on the watch face to get to the "Glances" menu
• Tap the airplane button to turn on Airplane mode
• Tap the airplane button again to turn off airplane mode
• Within a few seconds the watch will re-pair with the phone

Disable and re-enable Bluetooth on your iPhone. This fixed the issue for me. (This answer is just to give more visibility to the comment above by @tubedogg saying the same thing.)