Merriam-Webster defines guilt in part as:
Feelings of deserving blame especially for imagined offences or from a sense of inadequacy
A feeling of deserving blame for offences
Guilt can come from many places, it can be guilt for hurting someone else, guilt for not recognizing when you needed to step back from someone or something, or guilt for not stepping up or into a situation. For some guilt comes from the pain that others have caused them. Guilt for not recognizing that they were not treating themselves with respect. I carried a lot of guilt for allowing my father to abuse me as a child.
Guilt does have it's place, it is a way that we recognize when we have done wrong in society, and if responded to right away and amends made, it will set a pathway in our brains so that if a similar situation appears again to us, we can deal with it in a much more appropriate way.
However, nothing good will come from carrying guilt beyond its lifespan. Guilt will cause a breakdown of your relationships with others as well as the relationship you have with yourself. It will stop you from experiencing new things, from participating fully in activities, it will rob you of sleep, it can lead to anxiety, depression and if left to fester long enough, it can result in thoughts of suicide or self-harm. Some people who do not have your best interest at heart can use your own guilt against you to coerce you into doing something you may otherwise have declined. Acting out of guilt can only drain you further and could lead to resentment of the person.
Cognitive therapy can help when you carry guilt beyond its time. If you feel as though you have hurt someone, or know that you have, apologize, make amends however you can; but keep in mind no one can alter the past; what's done is done; you need to learn now how to move forward. In the end, we often assume that others have placed much more concern on our thoughts and actions than they actually do. So talk to them, and if they indicate that they are okay with the situation, then let it go. (Easier said than done of course)
God teaches us that guilt is a tool that the evil one uses to keep us from fully enjoying the life God has granted us. If we continue to carry guilt we will miss the blessings and small joys we have been given. We become self-absorbed and our focus becomes self-focused and not God-focused. The Bible talks about guilt and guarding against feelings of guilt in both the Old and New Testaments. David felt guilty over disobeying God, his friend and members of his army. God has given us a way to remove the unnecessary burden of guilt in our lives but we can not do it on our own. We need to give our full selves to Him and allow Him in his authority to cleanse us and make us new again.
Heb. 10:22 (NIV)
let us draw near to God with a sincere heart and with the full assurance that faith brings, having our hearts sprinkled to cleanse us from a guilty conscience and having our bodies washed with pure water.
So what about those times when we confess, we ask forgiveness, we have made amends and the feelings of guilt come back over and over? Does this mean God has not forgiven us? That we didn't do enough to earn forgiveness? No, not at all this kind of guilt - a guilt that does not leave even after we repent and turn to Jesus for cleansing - is not from God. Do not allow the evil one to steal your joy, your thirst for spiritual growth. The more you learn to ask for forgiveness, and accept forgiveness the stronger the attacks will be. The evil of this world doesn't want us to grow closer to God, he wants us to be in doubt, to live in the world.