It's perhaps inevitable that some of the romance will go out of a relationship as time passes.
And for some couples that spontaneity is replaced by a steady and deepening affection.
But not for as many as we would like to think. In fact, most couples are unhappy in their relationship, say researchers.
More than six out of ten adults in a relationship admit there is a lot they could do to improve their love life - and four out of ten admit they have considered leaving their partner. One in ten no longer even trusts their partner.
A study of 3,000 couples also showed a lack of sex, spontaneity, affection and romance makes it hard to maintain a loving relationship.
In fact, most couples only rate their sex life as being six out of ten - and 25 per cent claim activity in the bedroom is more perfunctory than perfect.
More than half of those polled said their partner was no longer the 'affectionate and giving' person they were when they first started dating.
And for 33 percent acts of spontaneity - such as booking romantic trips away, cooking a favorite meal or bursting in with a bouquet of flowers - are all but dead-and-gone.
'The sad fact of the matter is that when people first start dating, they go to great lengths to appeal to each other by being sexy, romantic and giving,' said David Brown of website UKDating.com.
'But once that honeymoon period is over, it is all too easy to start taking each other for granted. Once couples fall in love and settle down, they fall out of the habit of making an effort.'
The survey also revealed 13 per cent of couples no longer want the same things for the future and 19 per cent don't give each other enough time or attention. For 16 per cent a lack of time to talk is a bone of contention, whereas 7 per cent simply don't fancy each other any more.
Half of those questioned believed they were stuck in a rut with their sex life and had no idea how to re-create the passion they once enjoyed.
