If you haven't, I strongly recommend you to read this guide first: https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3003250312
It covers all the basics that can help you with most problems.
My guide intends to give a few extra tips but assumes that you are already familiar with the basics and are struggling specifically because of either fear or because you have no idea of what to try next.

I'll only add one more tip for those who are struggling with the controls.

- Lock your target. If there is no target to lock, the default will be the environment you're in.
- Match speed. That will make you motionless relatively to the target locked.
- Look in the direction you want to move.
- Move forward a little bit, just enough to start moving, then let go of the controls
- Match speed again to stop moving.
You should always cancel out your previous motion before trying to make another.

You will die. In reality, normally, just once. In this game, a lot. And that's okay.
Death does not mean failure here. It's just a minor setback. Litterally.
Once you're at peace with it, you can actually start having fun and let go of the pressure.
In this game, being afraid of death will only prevent you from learning important lessons.

Just to be clear, this is not a place to go on your first expedition. There isn't much to see there anyway. You should only go there once you know what to look for.
Throw your scout in the direction of a light and spam the "take photo" button until you see what it is, then recall your scout. You can do that for each light as soon as you enter any room, so that you know where the fishes are.

This place is pretty scary at first but actually not that dangerous. Being mostly water, there is almost zero chances of crashing your spaceship. In fact, Gabro will give you the following advice: "if you're caught by a tornado, try to aim for water". That's the most basic way to survive a fall in Giant Deep.
Appart from tornados, you have nothing to fear from this planet. Even though there are other things that might kill you there, it's nothing that you can't anticipate. All the other dangers are static; if you die, it won't be by surprise.

Very scary but actually almost harmless. As mentionned before, don't be afraid of death.
Meteors have very little chance of hurting you directly anyway, but if you want to stay clear of them, you should be safe around the north and south poles. You can also stay safely in you ship, way above the groud, circling around the planet looking for points of interest. Small hint: try to find the Nomai escape pod, it'll show you a way to stay safe from the meteors.

Note: I intentionally omitted something to avoid spoiling it. I don't have specific advice anyway, just stay curious ;)

Nothing scary there.

The sand column is only at the equator. Stay clear of that and you'll be fine.
Try to explore the Ember Twin early in the cycle, so that you get the maximum amount of time to explore before the sand fills the caves. If you know you're trapped, meditate. If you can't meditate, remove your headphones and wait for it.

The Sun is massive so getting too close will very likely end with your ship getting caught in its gravitational pull and falling into it. It happens to everyone. Don't trust your autopilot unless you can see your desination right ahead of you and make sure nothing will get in the way. Be extra careful if you're trying to get to the Hourglass Twins.
The autopilot is still a great tool for most simple usages, it's a very simple automation of 3 basic steps that you can actually perform yourself once you understand what it does.

Not that dangerous, nothing you should be scared of. The only thing you should worry about is it getting in the way while you're going from a planet to another. Avoid jumping and using jetpacks here as you can easily escape the gravitational pull of the comet.

Space is big. It can make you feel small. By many ways (which I won't tell because it would be spoiler), this game can make you think like life is meaningless and that nothing matters.
The only way to deal with it is to stop trying to find meaning and decide what you want to do instead.
In an indifferent universe, you're free to do what makes sense to you, to decide what is important to you.
I recommend this video (and this youtube channel by extension) that explain the philosophy behind these ideas:
https://www.youtube.com/watch?v=MBRqu0YOH14

If you're easily scared and playing this DLC, you're asking for trouble.
I can say that much: for the first half, you have nothing to be afraid of. You'll know when you made it to the second half. Hint: you're in the second half once you figured out how to lit a green fire.
If it's too scary, try enabling the option to make it less scary, or the usual tips for horror games: play in a lit room, play with a friend, remove headphones... anything that can help you remember you're playing a video game and not actually living the thing.

Try taking a break. Do something else, or maybe just pause the game and think calmly.
Almost every time I got stuck, I made it out on my first run after a break. The break should last at least 2h to be efficient, but nothing is as efficient as a good night's sleep.

Most of the time, being stuck is the result of one of these causes:
1. You're missing some information from another place
2. You made the wrong interpretation from a previous observation.

Challenge what you think you understood by going through the entries of the ship log.
I lost many hours trying to get to some place only to realize there was an easy way long after while exploring other stuff. I lost even more hours trying to accomplish something far too complicated near the end of the game because I made one failed attempt without understanding correctly why I failed.

It would be such a shame to get spoiled while trying to get a little hint online. If you really must get help, ask a friend that played the game to give you a hint. If none of your friends played it, maybe ask for help in Steam community and/or Reddit.