As you get older, having healthy relationships increases your quality of life.
The most recent research demonstrates how strongly we are affected by the thoughts and feelings of others. If we find ourselves in negative relationships it will affect us over time. Of course, some of this depends on how we chose to interact with those close to us.
In his book, "Social Intelligence," Daniel Goleman points out that we can catch other people's emotions in much the same way that we might catch a cold. Nobody can avoid being around negative people all the time, however if we have constant contact with such negativity, it drains our health and quality of life.
He goes so far as to say that good relationships act like vitamins and bad ones are like poison. This happens because the thoughts and emotional reactions we have affect our whole body, all the way down to our cells.
First of all, take responsibility for your own thoughts and emotions. Learning stress management techniques can go a long way.
Second, if you are in a long-term relationship, do work to improve areas where you are not happy. This might be as simple as sharing your feelings or asking the other person to share theirs. If this doesn't help, consider seeking professional help from someone trained in relationship counseling. You might choose to see a minister, priest or rabbi, or a psychologist or marriage counselor. This can often be very helpful.