Guilt is an emotion that can lead us to better ourselves. If an action causes harm to another, guilt, and consequently remorse, will lead to an apology, efforts to right the wrong and a feeling of not wanting to repeat the action and do better in the future.
However for some people, especially those who have suffered from guilt as a young child (we start to feel the emotion of guilt around age 3-5) and were unable to understand and articulate their feelings at the time, guilt can manifest when it is not warranted or deserved. When guilt starts to build in an unhealthy way, such as feeling guilty for thinking something negative about someone else, wishing ill thoughts upon others, or not reacting to a situation that was outside your control anyway, it can lead to self-deprecation, obsessive thinking and depressive thoughts.
Counselling allows you to share and explore your thoughts and feelings in a safe, warm and non-judgmental environment. Working through your feelings with a therapist can help you have a better understand of your guilt.