Whether you're in your first relationship as a teen or your twentieth as an adult, there are five definitive truths to every relationship.

Here's what you need to accept if you want to keep your relationships happy and your sanity in check, reports Daily Mail.

No matter how much your partner loves you…

THEY'LL WATCH PORN EVEN IF THEY'RE HAVING GREAT SEX WITH YOU

Most people past the age of 40 have come to terms with the fact their partner watches porn when they aren't around, at least now and then.

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As long as it's not being used as a replacement or becoming an obsession, it's usually seen as harmless.

Lots of couples also watch it together.

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THEY'LL KEEP ON MASTURBATING

There is a certain percentage of the population who believe that if their partner satisfies themselves solo, it means something is horribly wrong in bed.

If your partner isn't having sex with you at all or rarely - and only has sex solo – it is indeed a problem.

But masturbating means you have no-one to worry about but yourself: it's a simple pleasure release that's blissfully without judgement.

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THEY'LL STILL FIND OTHER PEOPLE ATTRACTIVE

Even if you think your partner is the most attractive person you have ever met in the world, it still won't stop you noticing other people's good looks.

Love and commitment stop us acting on this attraction – they don't stop us experiencing it.

If it really bothers you, do what I do: acknowledge the other person's beauty so they have permission to look.

Tracey says that almost everyone has sexual fantasies about other people, however pressuring your partner to talk about their's just causes paranoia. Photo / Getty Images
Tracey says that almost everyone has sexual fantasies about other people, however pressuring your partner to talk about their's just causes paranoia. Photo / Getty Images

THEY'LL FANTASISE ABOUT OTHER PEOPLE

Just about everyone has sexual fantasies: 90 per cent of women and 96 per cent of men have them daily.

Imagining something in your head is an entirely different matter than doing it in real life, but lots of people consider the fantasies a betrayal.

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Most people adopt the "don't ask, don't tell" policy with fantasies because most of us don't want to know that someone we love is having lustful thoughts about someone else.

THEY'LL HATE YOU AS WELL AS LOVE YOU

Even if you do every single thing right and never upset your partner - they would still have days where they feel resentful of you.

Or are bored by you. Annoyed by you. And yes, hate you as well.

Arguing is healthy: it means you're not afraid to speak up about things that upset you.

Love isn't a straight line. Even the best relationships have ups and downs.

It's indifference, not flashes of hatred, that kills relationships.