Mr Simmonds spoke about a relationship being two circles that overlapped at the centre. He said people did best if they had their own individual lives but were able to come together and complement each other.
Honesty and trust were essential.
"If people can be honest and vulnerable with each other then they can sort out any problem. Most people are afraid to talk about the real stuff ... because they don't want to hurt the other person. These are the ghosts in a relationship."
Mr Simmonds said it was important for couples to understand where the other person was coming from when disagreements occurred, even if they didn't agree.
His final tip for a successful relationship was to work at the relationship and do special things for each other every day.
"Even if it's as simple as bringing them a cup of tea in the morning."