Everyone feels down in their life, even if you have everything in the world. Even the baby, with its underdeveloped brain cries when it loses sight of its mother.
So you see that this emotion, where one feels some grief or sadness, or 'being down' is something that is a natural emotion within us. And this causes us to reflect over what it means, and can it be countered if it is ingrained in us?
It happens because something is not to our liking and it has disturbed our tranquility. It has given us a shock. This is even if we expected it. For example you're sure that you failed your exam, but when you actually get your results, you feel down. That's because we still maintained a glimmer of hope, deep inside us, and we had some wishful thinking that we'd pass. And now this hope has been destroyed, and a part of our dreams has been destroyed. We had put our trust in ourselves, or in some device or person.
So what's the point of the feeling? It basically makes us turn to Allah Most High, who has control over everything and who decides everything. It makes us realise that He is in charge, and that we should trust in Him. We shouldn't rely on ourselves, because we don't know when our body would suddenly collapse from a virus, nor should we rely on people, because we don't know their hidden nature, intentions, and their forgetfulness, the fact that you do them favours and be nice to them for years, but then they forget them all in a second and reject you, and you don't know what circumstances will suddenly limit them. Nor should we rely on technology, since you know how they suddenly can fail on you.
Thus we are forced to turn to Allah swt, since He is free from all imperfections, and He is and speaks only the Truth, and can do anything. He has no limits.
But if He did not give us this sadness, then many of us wouldn't turn to Him in trust, nor rely upon Him. We would think that our efforts etc are independent of Allah, because we'd think that our efforts etc never fail, and we'd be deluded.
Also if our problems are due to relationships with people, it reminds us of our relationship with Allah swt. How many of us have neglected our relationship with Him? Its like He is telling us 'I gave you this relationship with your family or spouse or friend, yet you forgot your relationship to me. Come to me my lost servant! I provide everything for you already, I will love you even if everyone hates you. I will look after you, even when everyone turns against you. I will be with you, even if no one is with you. I will give to you when you ask, even if no one gives to you. I will wipe away the blood from your face caused by those who harmed you, even when no one will feel pity for you. If someone hurts you, I will take revenge for you, even if no one stands up for you'
Plus feeling this sadness, unites us with the best of people, the Prophets, who also felt sad at times, like when the Prophet was beaten by his people and rejected by his relatives. And yet they were the best of people, and feeling what they felt, helps us become the best of the rest of creation.
So you see that this feeling helps develop excellent character, like it opens up our hearts in sympathy for others, gives us the chance to learn patience, removes the dunya from our heart, thus allowing us to be more generous. It allows us to do what is really hard, i.e. 'Being kind to even those who wronged and hurt us'. This makes the reward great. Plus it’s a mercy, since the Prophet said: “Whenever a Muslim is afflicted with a hardship, sickness, sadness, worry, harm, or depression --even a thorn's prick, Allah expiates his sins because of it.” (Bukhari)
Furthermore it allows people to fulfil this Hadith where the Messenger of Allah (may Allah bestow peace and blessing upon him) said,“There is no Muslim who consoles his brother upon a calamity except Allah will cloth him garments of honour on the day ofjudgement.”(Ibn Majah)
It also displays the fact that Allah swt is in charge, and can change our problems, and wants us to rely upon Him, is shown by the fact that when we are down, to the lowest of levels, we do dua to Him, we read His Qur'an, we do salah with utmost humility, need and sincerity, and we feel so happy, we feel our troubles go away. We feel like we are in a new world, in a new life, in peace, and calm. And by reading the Qur'an and thinking deeply over its meanings, we find the solutions to our own, personal problems. We get hope, energy and will to change our situation, by relying upon Him. Allah is speaking to us, so let Him touch our HEARTS.
He says ""Truly, it is by the Remembrance/zikr of Allah that hearts find rest/peace." (13:29)
But some people, they feel at this moment, that they must turn to other things. The shaytan puts thoughts into their head. He promises them peace and happiness. So he leads them to the wrong ways. However the Qur'an, from Allah the Pure, says “He [Shaytan] makes promises to them, and arouses in them false desires; and Shaytan's promises are nothing but deceptions [4:120].
The wrong ways/paths involve listening to haram music (like Indian, Korean and Western music etc, stuff that has no Islamic lyrics), committing adultery, drugs, violence and so on. These ways don't solve anything, they don't give peace, except maybe for a short period of time.
For example if you listen to rock music, or some singer talking about how he misses a girl, you feel like moving your body like crazy, or you think 'oh he knows how I feel', so you find peace in that. Or you might even feel more sad. But it doesn't change your situation or problem. The music doesn't tell you how you can get out of your problem. Often it won't even give you hope, nor the needed will. People turn to music and other things, because their hearts have become hardened and rusted, so they are less affected by the Qur'an. But they should turn sincerely, repent to Allah swt, and cry to Him that He opens up their hearts heart. They should abandon their sin, take good, righteous Muslim company, go to gatherings where Allah swt is remembered, seek His aid and read and reflect over the Qur'an.
In fact by turning to the haram ways, like haram music, you end up increasing your sins. Anas (Allah be pleased with him) reports that the Messenger of Allah (Allah bless him & give peace) said: “On the day of Resurrection, Allah will pour molten lead into the ears of whoever sits listening to a songstress” (Recorded by Ibn Asakir & Ibn al-Misri).
Some people even die when they're really down, for example they're less aware when they're driving or walking, that they crash. Or they get a heart attack, because of their stress and worries. So you would want to be increasing your good deeds, not bad deeds right?
The Prophet (Sallallahu alaihi wa sallam) said: 'A place in paradise as small as the bow or lashes of you is better than the world and whatever is in it.' (Bukhari). So don't lose hope in this world, but look at the hereafter.
Thus if we look at our tests, and worries, and feelings in the correct perspective, we recover from these feelings/tests much quicker, and we get a lot of reward and become better people insha'Allah. Remember to let Allah swt touch our hearts through the Qur'an.