Pairing everytime topic

Mostly in night i put my g watch into airplane mode to save battery and turn off phone's bluetooth and in morning when i turn the bluetooth on and airplane mode off on watch i always need to repair the watch with phone a notification pops up to confirm the pairing with th pairing code, whereas my friend's watch simply connects automatically he doesn't need to do anything, why is it so, i m on 5.0.2 on both fone and watch the problem is same from the kikat time, does anybody know anything about this

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