Is Arguing Good for a Relationship?

Jared and I never ever argue. I always thought this was a good thing. We always seem to come to conclusions together and things never get heated. We rarely have ever had those nights that you just go to bed angry with tears dried to your cheeks. Even on a lesser level we rarely ever disagree. We usually are pretty "chill" and always just go with the flow. Nothing stirs us up. Our household is always a calm place. I really thought this was good, but now we are a year and a half into our marriage. Things have certainly changed from when we first started dating. Of course, there's more responsibility with being married, sharing all the financial stress, and making decisions together instead of separately  We've been seeing a therapist to  help with certain things that have popped up like anxiety, coping with severe A.D.D and building a healthy marriage that will last. I mentioned to her that we don't argue. She thought it was extremely strange because we've been together for 4 years now, and then she asked if we have disagreements, and our answer was not really. She was floored that we claim to not disagree.
In her perspective, she thinks it good to argue, don't be confused she doesn't want us to have these drag down fights, but just to voice our own opinions. It helps keep individuality and keeps resentment out of our marriage. When you are not disagreeing then either you are caving or your spouse is caving. One of you is not getting what you want in certain situations. Of course, there are PLENTY of things that you agree on, but for those that you don't it's okay to say just that.
An example: If your husband wants a guys night and you really don't want him to go because you don't feel well and think it would be nice if he stayed home, but you tell him "Yeah, go out - no worries!" You may hold resentment for him not "sensing" that is not what you really wanted. That's you caving and not being honest and it can lead to a worse argument or resentment.
I do a lot of the whole "Yeah, go out - no worries!" In my head I want to be a rockstar wife. I don't want to be clingy and I don't want to be needy, so if I were to ask him to stay home I would feel like just that - a clingy needy wife. PLUS I don't want to disappoint. If Jared really wanted to go out and I said no, he'd be confined by me and disappointed that he missed out.

Our therapist thinks it's great to always be as honest as possible, which may result in arguments. I hate arguing. I never grew up around arguing and I don't know how to do it well. I don't know how you resolve an argument, this probably also plays into my fear of confrontation. Which is most likely why I steer so clear away from any disagreements.
Do you argue with your lover? Is it beneficial?