If you have made mistakes in your relationship, your partner might harbor feelings of resentment that have not been fully expressed. If you betrayed your partner's trust, it can take a long time to rebuild what you once had. Even if your partner seems to have forgiven you, you might still feel guilty. You might also fear that your partner no longer cares as deeply for you. These fears might cause you to either lash out in anger or behave timidly if you fear an angry outburst from your partner.

If you find you are spending time thinking about your partner's transgressions, chances are there is an unresolved issue. You might have accepted your partner's apology but find you can't stop dwelling on the issue. If you are reluctant to raise the issue with your partner, your unexpressed, bottled-up feelings could result in depression or anxiety. Withheld feelings can also lead to a variety of psychosomatic symptoms, including headaches, ulcers and asthma, writes Rekha Shrivastava, a rehabilitation therapist, on the Cognitive Healing website.

Unresolved issues from past relationships can impact negatively on your present relationship. If, for example, a previous partner cheated on you and you never understood why, you might still feel distrustful of new people. If you wronged someone and neglected to apologize, your unresolved feelings of guilt could make you feel unworthy of true happiness. Seeking out people from your past, making amends or finding a way to understand and forgive them can help you move forward in new relationships.

Traumatic incidents that occur in childhood, such as a bitter divorce between parents or the death of a parent or sibling, can leave unresolved emotional scars. The Adults Surviving Child Abuse website warns that survivors of childhood abuse often experience problematic adult relationships. Because experiencing childhood trauma erodes feelings of trust and safety, survivors often find it difficult to build healthy attachments in later life. Professional counseling helps survivors of childhood trauma understand the impact of their past experiences on their adult lives and enables them to move forward in healthy relationships.