I was infected at dinner last night. No, it wasn’t salmonella from bad lettuce. It was the infection that comes when you’re with someone who radiates positivity and enthusiasm. My husband and I had dinner with a lifelong friend who recently transformed her life, and her exuberance was infectious.

For decades “Elizabeth” put on a brave face, soldiering through a troubled marriage and the assorted challenges that come with raising children and keeping them on track. She was the pillar of the house—providing, doing, sourcing for all, medicating herself with food and drink to ease her inner turmoil. But now her children are on solid footing in their adult lives, so Elizabeth decided it was time for her. I have been looking at her delighted Facebook posts for months—lovely photos of her new neighborhood…sunsets from her balcony…and a series of selfies showing her thinner, healthier self.

I have always enjoyed being with Elizabeth. She’s super-smart, super-curious and super-caring. But when we saw her last night, she was giddy. Our dinner could have lasted far longer but for the fact that my husband and I both had work to do before rising early to catch a flight home.

It was the kind of get-together that leaves you fueled and excited in your life.

Contrast this with the countless interactions I have had throughout my life after which I feel as if the life has been sucked out of me. You know the ones—someone spends the night complaining about the sorry state of his/her life…or talking-talking-talking but saying absolutely nothing…or looking for advice and then making excuses for why none of the suggestions offered would work. Awful, right?

Thankfully, the older I am, the fewer life-sucking experiences I have.

It takes a lot of courage and confidence to navigate these relationships, trying not to hurt the other person’s feelings while preserving your own sanity. It’s especially difficult for young people who have spent the majority of their lives being told by parents or teachers to be nice to one another and play with all the children in the class. To their credit, these young people actually heeded the advice, and now it’s difficult for them to realize that maybe some of those people they’ve been hanging around with aren’t really helping them feel—and be—great.

What to do?

Be aware. Sometimes we are so accustomed to being the good friend, that we don’t realize how empty or frustrating an interaction is. Think about how you feel when you are with that person. Does conversation flow easily? Are you watching the clock, planning your departure? Is your body relaxed or tense? Has your neck or back tightened during any of the interaction because of something that was said that makes you uncomfortable at your core? I don’t mean friendly debate or constructive discussion of frightening situations such as how to protect your kids from the drug epidemic. I mean something like a friend who is cheating on a spouse and proudly telling the tale…or someone who was and still is a “spoiled brat.”

Develop other friends and activities. You can’t let go of someone if you don’t have others to go to. If you’re holding on to your bestie because he/she is all you have, then you need more. Join clubs. Volunteer. There are a zillion ways and places to meet new people, including websites such as FriendMatch.com, the friend version of a dating site.

Let them go. I know this is not easy, especially for the people who have been in our lives forever. Letting go doesn’t mean that you have to confront the person or formally “fire” him/her as your friend. Nor does it mean that you must excommunicate them from your life entirely. Instead, simply tether them out, reducing how often you see him/her and for how long. Over time, the line can get longer and longer until they’re either gone or at a long-enough distance that it doesn’t hurt quite so much to spend time with them.

Don’t feel guilty. It’s cliché, I know, but putting that oxygen mask on yourself first holds true in so many situations. Life is short, and your time is limited. Do you really want to spend it in situations that make you feel bad?

One parenting message I have tried very hard to instill in my children is, when selecting friends and life partners, you need to find people who help you be your best and who bring out the best in you. When you’re surrounded by that kind of fuel, it’s remarkable the magic that life can be. Just ask my friend Elizabeth.