In today's world of having millions of strangers accessible at your very fingertips, it is more than selfish to expect your spouse not to look and admire other people. At the same time, something has to be said for appropriate conduct and clear lines of delineation of what is acceptable and what is not. There are ways to admire someone's beauty without being disrespectful to your spouse including commenting and leaving emojis. We all know certain emojis are sexually suggestive and I'm almost certain I don't have to spell out which ones. Getting someone's number who has no relation to your life and texting them is cheating emotionally. Just exchanging numbers is a strong indication that you plan on taking the situation further even if you don't have malicious intent. When I say in relation to your life I mean if you're exchanging numbers with a co-worker for reasons of letting them know your late, a classmate to get the homework or a mentor in your field of work. If you feel like something you're doing should be hidden, then you know damn well you shouldn't be doing it.
To dig deeper, if you are looking for something on social media it's obvious you are missing something in your current situation. Whether it be the excitement has dwindled with your spouse, your job/ money situation is not what you want it to be, or you're bored with life in general what you're seeking more than likely can not be found in cheating on your spouse.
There are ways to be vocal while simultaneously inspiring change. If you are no longer attracted to your spouse because they are fat, simply calling them fat won't change the situation. Inspiring them to do more will. Suggesting making life changes and doing fun work outs will inspire them to change. If you feel like life is boring suggest something fun.
In the same breath, the world is constantly turning, changing, evolving and so are our lives and our relationships with the people in it. It is selfish to assume that a flower won't grow or wither and die and will stay exactly the same. This analogy is how you should treat all your relationships. If you nurture it, take care of it, love it, it will grow. If you neglect it, it will die.
On the other side of your thoughtless boredom, there is someone who thinks that you are their world. They worship and love you. They have been with you for years, seen you at your best and your worst. They can feel a change in you and if your behavior persists they will pull away from you. Nobody deserves to be an after thought if they put you first. The bottom line is, If you want to step out then just fucking leave. It is unfair to cause mental anguish to someone because you insist on being childish and playing the field.