You are unfortunately only lying to yourself in thinking your not guilty as well.
This is a painfull time of year for many people and families, there is more than enough hurt to go around,but in order to avoid future hurt with your partner you need to take advantage of this and use it as "jumping on" point to start a meaningfull productive dialog about what you both did and did and why ?
Cheating happens when someone isn't getting what they need in there relationship ( I am eliminating a sexual addiction because from what you say it was once). I can understand your "revenge cheat" it happens more than any of us could really know because its not something you tell someone well having coffee casually .
What is obvious is you really don't know your partner as well as you should , because a relationship, partnership or marriage is very much give and take and openness of sharing yourself with your partner , it not share when it's convenient or when times are good , its share always , so when things completely suck you have someone to ease the load ,and to rejoice and celebrate when things are better. So break out the honesty and talk about this now before it happens again , find out what need your partner had that you were not meeting and why , how can you do better & how you both communicate these things so you can grow together instead of apart .Make this a happy holiday season as communicating partners with hope for the future together you are a whole , sort this out now , wounds fester and grow worse , you need to get to the bottom of your relationship so you can build it up , you cannot build a house ,a bridge, or a relationship without a foundation of honesty & love ,if you don't find yourselves now you won't later either .So this is your opportunity to advance your relationship, by finding out how and why you got here and where are we going from here . I am experienced both in relationships in my own life and as mediator trying to turn irreconcilable differences into hearing what each others needs & wants are and listening to what each other is really saying( you'll need that so when your old and gray you can finish each others thoughts silently or to others)
Wishing you the best ,and hoping you will do the rest in your words to your partner.
Sent from my SM-T810 using Tapatalk