Human beings have a natural tendency to hold on to other people or things that are important to them, because those people or things fulfill their needs, wants and desires.
When these people or things remain stable in our life, we feel comfortable and safe because our life feels enriched and fulfilled.
Should, however, circumstances suddenly change and we lose those important people or things, the needs, wants and desires that were once being fulfilled enter into a state of unfulfillment.
As a result, this loss causes us pain, which subsequently leads to the feeling of sadness.

How sadness affects you will vary from person to person, but chronic sadness, such as that resulting from the death of a loved one, commonly leads to addictions (e.g., alcohol, drugs, food), social withdrawal/isolation, martial breakdowns, depression and suicide in an attempt to escape the uncomfortable feelings that one is experiencing.

The feeling of sadness tells you that you have lost something which is important in your life. By feeling sad, you are made aware of that loss, which then makes it more likely for you to take some kind of action in order to get back or replace that loss.
This action comes from the motivational energy that sadness gives you, and if used correctly, will enable you to overcome your sad feelings.
How to Deal With Sad Feelings
Use the following guidelines to help you deal with the feeling of sadness and respond appropriately to it.
1) Identify the Feeling
Sadness comes as a result of losing someone or something which is important to you.
2) Remember the Meaning
The message sadness tells you is that the loss you have experienced has resulted in some of your needs, wants or desires no longer being fulfilled.
Sadness is motivational energy which is trying to help you to fulfil these needs again.
3) Decide Why You Are Feeling Sad
What have you lost in your life that is important to you? Why was it important? What needs, wants or desires did that person or thing fulfil? What did it/they do for you?
4) Do Something to Change Your Feeling
The first step in overcoming sadness is to examine how you currently view your loss. Have you really lost something or someone for good? Or is it possible that you will be reunited with them again sometime in the future?

For example, if you believe in life after death, then the loss of a loved is no longer a permanent loss. But rather, a temporary loss until you are both together again.
This hope of regaining what you have lost can help you to overcome your sadness and move onto grief without your life being adversely affected by chronic sadness.
So whenever you are feeling sad, always remember to examine your perspective of it first. As if there is hope of regaining what you have lost, you will be able to minimize the sadness that you feel.
Getting Back What You Lost
If there is some chance that you can get back what you have lost, try to do something to get it back.
For example, if you have lost somebody’s friendship because of something you did, try to do something to make up for it. There is no guarantee that you will get it back, but if you don’t at least try, then you will know for certain that you definitely won’t get it back.

If you are unable to get back what you have lost, you will need to find a replacement for it. How you go about doing this can vary depending on whether you have lost a person or a thing:
People
If your loss is to do with a close family member, then it’s important to understand that people like this cannot simply be replaced the way we replace lost items by buying a new one.
As a result, you may feel this loss for the rest of your life whenever something triggers a memory of that person.

However, you can still take action to fulfil your needs by forming new relationships with other people. For example, finding someone to talk with, go shopping with or play sports with.
By bringing new people into your life to replace the person you lost, you will satisfy your unfulfilled needs that came from your loss, thereby preventing sadness from negatively affecting your life.
Things
Fortunately, things are a lot easier to replace than people. So if you have lost something which is important to you then your first step should be to try to get it back.
For things that you can’t get back, such as unique items, try to be thankful for what you still have.
Usually, it’s not until we lose something important to us that we realize how much we took it for granted. This then causes us to become more grateful for the things we still have.

Another way to deal with losing something of importance, is to try to see what good came from the situation.
Sometimes, when we think something really bad has happened to us, something good happens as a result of it. If you are able to see the benefit from your loss, the sadness that you experience will be greatly diminished.
Summary
Sadness comes as a result of losing something important in your life and the needs which were once fulfilled by it. If you ignore your sadness, then these needs will remain unfulfilled and your life will suffer as a result.
Listen to sadness by finding a way to satisfy your needs again. This can be done by getting back what you have lost or by replacing it with something else.
Overall, just remember that sadness is a natural part of life, and you cannot control or predict when you are going to feel sad. The only thing that you can control is how you let that sadness affect your life.