There is something that you must understand about people - they will let you down. And the more you love a person, chances are that they will really hurt you when they do. This is just the way life goes, and the sooner you understand this... the easier the ride will be. Plain + Simple.
Before you start getting all ''Stop being so pessimistic, Kara'' just hear me out. Nobody is perfect. I am not perfect and you are not perfect and the guy you work with isn't perfect either. Neither is your kindergarten teacher who you loved so much and look back on with nostalgia from time to time. We make mistakes, and if we're lucky we grow from them. And realizing that sometimes people you love let you down can only help you learn from each and every painful experience you encounter. It's only been 24 years on Earth for me personally, but I've had my heart broken and stomped on too many times to count. Sometimes, admittedly, I've done the stomping.
Sometimes, life throws a curve ball and it knocks you unconscious for a few minutes before you get a chance to shake it off and try all over again. The important thing is that before you shake it off, you really feel that pain and accept it before trying again. You should always strive to feel every moment of life, and know that accepting these not-so-fun emotions is not the same actual thing as being okay with it. You have to be able to admit that you aren't in control, and that sometimes you get on a roller coaster and you can't just throw your hands up and yell "STOP!!!"... you have to actually ride it out and then decide if it was worth an extra go-round or not. Sometimes it is, other times it isn't.
But when you are in this moment of disbelief and overall hurt, breathe it in and then breathe it out. When you do this, you are more capable of learning from it. You have time to think about why this person let you down, what they were thinking, what was going on in their life, if their past is influencing them at this moment, if yours is. You can say: This hurts. But I know that they love me and I see where they were coming from, and I trust that they weren't intentionally inflicting this pain on me because our past history reminds me that they care about me just as much as I care about them.
You can also say: I keep getting hurt by this person, and I want off the roller-coaster.
In both instances, you have looked at the situation from all sides and felt the emotion and made a decision. This is living in the moment. Every moment. Not only happy moments, and not only sad moments, but every moment without skipping over some. Because there is something that you can learn from each and every moment of life, and learning only makes you grow as a person and aware of things that you hadn't considered before.
And while you're living in this moment, that sometimes isn't so fun, it's important to remember that there are other things in your life that are not letting you down. There are other friends, husbands/boyfriends, opportunities, chances worth taking, adventures to begin. So rather than dwelling on something sad, feel the moment and learn from it and then move on. You can choose to take the thing that hurt you along with you for another ride (sometimes the ride isn't so bad once you've experienced it, and it becomes your most favorite thing), or other times you can get off of the scary roller coaster (that continues to be scary, no matter how many times you try again) and find something a little more pleasant, like the merry-go-round instead.
The Universe has a lot to offer in each and every moment, and it is our job on Earth to learn from her lessons and better ourselves and those around us. Living in the moment is easy, when you recognize the opportunity that is being offered and the chances that are worth taking.