Close personal relationships have, at their centre, a core of trust and vulnerability. In order to become close to someone, you have to open yourself up to them and share your hopes and dreams, failures, triumphs, failings. This happens as a necessity when you spend so much time together.

When you share these things, you make yourself vulnerable to the other person. You are essentially trusting that other person, saying "I will share these things with you, and I trust you not to hurt me when I do".

So when you have a close, trusting, vulnerable relationship with another human being, an act which shows blatant disregard to your feelings, with the knock-on effects of hurting your relationships with other people, your quality of life, your ability to trust in the future... well, it's like shyly showing someone your most tender spot and having them stab you repeatedly with a knife. Laughing and having fun when they do so.

My ex-husband cheated on me. As a result:

• I lost a lot of relationships. I no longer talk to his mum, dad, step-dad, step-mum, four sisters, aunts and uncles, cousins, grandparents, etc. I lost ten friends who I thought were wonderful people. I miss all of these people, quite a bit. They were my adopted family.
• I lost the future I had planned. I may not be able to have children now, I've left it too long.
• I lost a lot of money.
  
• I lost my best friend (at the time, he was my best friend). That left a very big hole in my life.
• I lost a great portion of the things I used to do and the places I used to go.
• From the emotional turmoil, I lost a lot of mental focus. I'd say about six to eight months of emotional turmoil.

So, from that one act, I lost family, friends, money, and future.

He was capable of doing that to me in two evenings of drunken boundary crossing. He didn't care at all what happened to me. And if he find this now, and reads it, he will probably laugh at how stupid he thinks I am, how I deserved it for being a credulous, gullible cow.

Luckily for me, I found the most amazing, kind, sweet, trustworthy man just waiting for me to lure him into my clutches a couple of months afterwards, and I am trying to rebuild. I actually have more friends now. I still find myself wary, though, and I haven't fully opened myself up to him even though he's the one who actually deserves my trust.