Deal With Guit

Feeling guilty is almost as bad as feeling heartbroken or depressed. It can nag at you for ages, and ruin your fun. The best approach towards guilt is to sort it out and clear your head.
Try to figure out why you feel guilty. Grab a pen and notebook, and write down a list of things that could be making you feel this way. It might be difficult, but eventually you will figure out what is making you guilty. If you can't figure it out, try this approach: Consider each thing on your list and imagine if you had not done it. If you immediately feel better or wistful, this is probably the thing which is making you guilty.
Rate your guilt. This might sound stupid, but it can really help. Out of ten, make two ratings: How bad the thing is that you've done, and how guilty you feel. After this, think about why what you did was bad, and why you feel guilty about it. This should hopefully leave your mind a little clearer.
Consider what you are going to do. If the guilt you feel is over something like being nasty to someone or neglecting a job or pet, feel reassured in the fact that you can do something about this. Write down what you're going to do, consider when and where, and take action. If your guilt is for something like a persons' death or a friend getting angry, acknowledge that it is not your fault, and it's natural to feel this way. Do something to relax and forget about it.

Everyone messes up sometimes. If the person that you commited the wrong to is your friend, they will forgive you in time.
Try not to keep secrets from your parents. Things will only get worse if you become further apart from your parents.

Don't hold it in. It will constantly bother you all the time. The best thing to do is tell someone about it.