Too often relationships are seen as the long hoped-for source of happiness and joy. The thinking goes along the lines of: "Only when I have found 'the one' will I be truly happy and fulfilled." In other words, the relationship, and in particular the loveable other, is seen as a continuous supply-chain for a lifetime of happiness and delight.
The problem with this way of thinking and behaving is that it puts the onus on the loveable other to deliver - all the time. To go into a relationship with an expectation that it will supply a lifetime of joy, is to go into the relationship with needs. I need you to do this. I need you to be there. I need you to behave and speak in ways that support me. Quite simply I'm bringing my big bag of needs and expecting you to make them go away.
However no relationship can do this. No one person can do this. If a relationship is built on two people getting together based on neediness then watch out. That relationship is destined for a short shelf life. Everyone is on the take and very soon the relationship is starved.
Because relationships are based on giving, not taking. Whatever you give to a relationship, you get back. If you go in giving demands and problems then don't be surprised when you get back demands and problems. Just like a mirror, a relationship will always reflect back to us what we bring to it. All relationships have a personality that is defined by the individuals that make up the relationship. When your starting point is one of "what can I give?" then you transform the nature of all your connections.
The key to successful relationships is to go in with the ability to give that which you want to receive.