A piece on how pitches could be won or lost on "relationships" had my neck stiffening and my heart sinking recently. I can talk at length about value managing relationships (VMR) and why VMR is a good emotional contract for successful, long-term business. But that's the point: trust, based on mutually agreeable commercial goals, is at the heart of the relationship not an airy promise about feelings.

If you can demonstrate, at pitch stage, you will manage the new relationship on the basis of tangible value and return, good for you and you have a chance of winning. But the suggestion you can create a deeply meaningful client-agency "relationship" from Day One is flawed thinking and a dangerous promise.

Strong relationships are based on trust and trust takes time and a number of interactions to develop. It is not something to be kept in a bottle and sprinkled lightly over the boardroom table as the prospect enters the room.

A good party never saved a bad agency.

Relationships begin to crack the moment promises are broken. You win the pitch and two months later the key account director decides to travel the world/join the competition/go in-house. It's a broken promise as far as the client is concerned – who hasn't known the agency long enough to trust management to make an invisible mend with the perfect new recruit or substitution. Confidence and certainty will only develop over time (quite a long time) as well as genuine comfort with the agency's culture and staff management processes.

There are always arguments about keeping the client happy and how important the "relationship" is. Glastonbury, anyone? The theatre, lunches, dinners, a job for the godson or daughter – none of this will save an agency that fails to do the right job. These days entertainment is a dodgy area anyway, but even in the heydays of lavish corporate hospitality, a good party never saved a bad agency.

I was once asked by a wise mentor whether I thought our agency was selling "happy people" or "happy clients". (And I still ask this question when handling agency searches for clients). The answer to my mentor was "happy people" – but I wasn't running an agency in those days and he disagreed.

I thought he was awfully tough. Years later I realised happy people are only a given when happy clients are on board. It is happy clients that keep an agency able to provide the opportunities, the TLC, the training, the growth, the stability and the market leading compensation that successful work ensures.

An even tougher example is the terrifying answer to the question: "Why do you want to get into PR?". Sometimes the answer comes back: "Oh, because I get on really well with people". And you know, deep in your heart, that this poor child will be happier raking leaves than coping with the pressure and stress of managing a decent agency-client relationship throughout the intensity and turmoil surrounding the delivery of successful and profitable public relations work.

Written by Jackie Elliot, CEO of communications firm Cathcart Consulting