Some friendships are the type that offset on the playground or before we tin fifty-fifty think — and last through graduations, moves, marriages and all of life'south ups and downs. These are the friends who may or may not be in our everyday lives, but we know they'll always be there when we need them and they'll always care.

Most friendships, however, aren't that type, says Suzanne Degges-White, PhD, Professor and Chair of the Department of Counseling at Northern Illinois Academy and author of the books, "Toxic Friendships: Knowing the Rules and Dealing with the Friends who Break Them."

"We modify and our friends change over time — as do circumstances and new social goals," Degges-White tells NBC News BETTER.

That means some friendships morph over time (after people get married, for example, plutonic friends outset to fill different needs in our lives) and some friendships just fizzle out and end.

Why Friendships First and Why They End

I of the biggest reasons we become friends with people in the start identify is physical proximity, explains Mahzad Hojjat, PhD, Professor of Social Psychology at the University of Massachusetts Dartmouth and co-editor of "The Psychology of Friendship," says.

"We tend to get friends with people who nosotros see a lot," she explains: people who live near us, work with us or people we do activities with. (Numerous studies back this upwards.)

"And nosotros tend to get friends with people who are similar to u.s.," Hojjat adds. People who are like united states tend to like us because whatever we share helps validate our own tastes, values and preferences — and fill a practical demand, Hojjat says. If we both like to play tennis, if we become friends we have a new tennis partner. If we like horror movies, we now have someone to sentry them with.

And throughout life, the roles our friends play in our lives likewise change. For example, when we get married or get parents, we demand friends who do the aforementioned because nosotros bond over the challenges those changes bring.

People who are similar united states of america tend to like u.s. because whatever nosotros share helps validate our own tastes, values and preferences — and fill a practical need.

But, for nevertheless reasons friendships begin, friendships terminate, besides, Degges-White says. "When [a neighbour] moves abroad, the friendship might 'movement away,' likewise. … And at some point those 'soccer moms' might not exist the friends that we need any longer — or fifty-fifty desire anymore."

Some friendships will inevitably just fade away when circumstance like a job changes or y'all finish going to those kickboxing classes. And in other cases, you may be better off intentionally putting less effort into a friendship.

What'southward the Correct Time for a Friend Breakup?

If a friendship does starting time to feel one-sided — that you're the one constantly reaching out — it's a definite sign that something may be up and that relationship may not be as healthy as information technology could be. Ask yourself: Are y'all improve off with them or without them?, Degges-White says.

Here are a few cues it may be time to invest a little less:

  • The large no-no's: If someone is stealing from you, spreading rumors, lying to you lot or not supporting yous, those are all pretty major transgressions that break the commitment that fundamental define what a friend is, Hojjat says.
  • If at that place's more negative than positive: At that place shouldn't be more wrong with a friendship than there is right, Hojjat says. "Spend time with people who truly care about you and are supportive."
  • You feel worse, not better, later spending time with a friend: Certain we all might get caught up lamenting a piece of work problem or breakup from time to time. But when interactions are repeatedly no longer fun, have annotation, Degges-White says.
  • Your friend has no redeeming qualities: Peradventure a friend is ever upward for a round of golf or they're the neighbor who'll catch our mail when we're away — fifty-fifty if we don't similar everything nearly that person, Degges-White says. But if y'all're non getting annihilation out of that friendship and it puts you in a bad mood, be wary.
  • If a friend is constantly putting you off or canceling plans: "You tin can forgive the first fourth dimension or two, simply if the pattern continues you need to decide whether this is [your friend'south] way of cut you out," Degges-White says — or detect out if something else is going on.
  • If you find yourself ignoring texts, not returning calls, and non wanting to detect time in your schedule for a person: That's your own red flag the relationship isn't bringing yous what it once did or ought to, Degges-White says.

When to Cut Your Friends Some Slack

The caveat is, don't give up too apace, notes Hojjat. Some people do accept a trend to withdraw if they're going through a tough time (a lost job, divorce or some other problem), she says. "If you're really interested and committed to that friendship, exhaust all reasons why that person is non calling you back or reaching out before you call it quits on the friendship. Stay resilient."

Sometimes you just demand to cutting your friends some slack, adds Degges-White. "All of us hit rough patches in our lives when nosotros get defenseless up in our own 'stuff' and have lilliputian fourth dimension left for friendships or other leisure pursuits."

And finally sometimes adjusting your expectations for the relationship helps, but you don't have to cut out that friend completely, adds Irene S. Levine, PhD, Psychologist and Professor of Psychiatry at the New York University School of Medicine. "Take the positive aspects of this friendship and look to other people to fill some of the gaps."

And remember: E'er be thoughtful about ending friendship, says Levine. It's harder to become rekindle a friendship after y'all've striking the brakes.

Merely don't experience guilty nearly cut ties when a friendship isn't worth information technology, Degges-White adds: "If yous've given the human relationship a off-white chance and you are just not getting what you lot need from the human relationship, it is absolutely okay to motion on."

Want more tips like these? NBC News Better is obsessed with finding easier, healthier and smarter ways to live. Sign up for our newsletter and follow us on Facebook, Twitter and Instagram.