It’s the small things that count. Lots of small little things. Things that the other may not even know you did.

Like not eating the last piece of cake just so your spouse could have it.

Like not bothering him/her when s/he is reading.

Like bringing him/her a cup of cold water – without being asked. And then taking the cup back for a refill.

Fixing the thing that is broken. Without making a big deal about it. (This one is for the men.) Telling him/her something you are proud that s/he does.

Put your phone down when you speak to him/her. For the whole conversation.
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You know what your spouse would so appreciate from you.