In the way of mental health, someone's personal struggles may not always be apparent.
You cannot always tell when someone is feeling extremely down, or extremely anxious, or otherwise not quite right. For some, mental health is something apparent and something which makes itself known to those around them. For others, though, this is not the case. Some people may be more private, and maybe just... well, more devoted to putting on a facade and wearing a mask, so to speak. For some, showing their true feelings is an intimidating thing, and because of this, they might be driven to hide their pain.
This, in short, is why it is so important to check on your "strong" friends. I have placed strong in quotation marks because I think that a lot of times, we make this assumption that someone is so strong that they don't experience pain in the way that the rest of us do, and realistically this could not be farther from the truth.
Sure, some people really don't find themselves in a place of deep sadness in situations where most people might, and sure, some people simply don't experience/are not affected by their emotions quite so much. However, the majority of people are, regardless of how things might seem.
There's a saying that tells us that sometimes the people who laugh the most and seem happiest on the outside are actually the most unhappy on the inside. This idea was widely discussed following Robin Williams's tragic suicide, for example, but I feel that it is something we need to keep in mind at all times, not just when Access Hollywood and the latest tabloids decide to half-heartedly remind us. Just because someone appears to be happy, does not mean that they truly are okay.
Similarly, when someone experiences a major, tragic life event, that person's pain might be very evident, or, conversely, the person may not seem to show much emotion at all. In both cases, though, this is someone who is very much in need of support, comfort, and company. Some find it easier than others to pretend everything is fine, but this does not by any means mean that everything actually is fine.
Let's start with the basics. Check on your friends. Just... you know... as a friend. Healthy, strong friendships are built between people who are there for each other, but more importantly, people who make it known that they are there for each other. Telling someone you are there for them is one thing, but actually being there for them is entirely another. If you say it, do it. Follow through with your words.
But seriously, just check on your friends. Check in every now and then and see what's up. Its honestly common courtesy, especially when these are people who play such a large role in your life.
More specifically, when you know someone you care about is going through something, check in on them. Even if they seem fine, even if they're laughing along with you and acting normal, just check. You never know what is going on in their head when they are alone behind closed doors, and it doesn't hurt to remind them that you care.
As someone who has been through some things over the course of the past year, I cannot even express how much it means to me when someone takes the time to reach out and check in, send some good vibes, or even just say hey and make small talk. When you are going through something, it is easy to start closing yourself off and getting drowned by whatever pain you are feeling, and this, as it turns out, is an extremely lonely way of living. Once someone finds themselves stuck in this lonely spiral, it can be really hard for them to get out, especially if they have found themselves playing the role of the "strong one".
Moral of the story: take care of each other. Be there for each other when you need it, and even when you don't. Remind those you love that you love them and are there to support them. You never know how much it might mean to them at that moment.