You're the person everyone goes to for advice. If someone needs you at 4 AM, somehow, some way, you'll be there. You're always there, whether it's at 4 AM or 4 PM. You always find a way to get back to them in a timely manner, no matter how busy you are. But being the strong friend is not an endless supply of empathy and sympathy to give out at any moment - in fact, it's a pretty tiring job. Everyone needs a shoulder to cry on, and usually, you're that person. For most people you know.
No matter what the situation is, you'll listen. Whether it's an issue with family, friends, illness, or more complicated matters, you'll always listen. Even when you have your own stress. Even when you have to get up at 7 AM. Even when you are facing your own life changes and are forced to put on a brave face. It's certainly an exhausting job title to have. It pays in the form of friendships and close relationships, but feeling fatigued is also a part of the paycheck.
Another part of you wonders - when I'm sad and drowning into my own head, who do I go to? Everyone has always come to me, and you know what they're dealing with. You would feel rude talking to them about your problems. You might even downplay your own problems for the sake of being a supportive friend and not venting too much or overstepping your boundaries. This is the cycle of being the strong friend.
Check up on your strong friend. They might be too guarded to tell you what's going on or how they feel. They probably don't want to tell you because they know all too well how hard it is to listen to people's problems. There's a million and one reasons why they won't want to talk.
But that's where you come in, friend.
Ask them how they're doing. Ask them if there's anything on their mind. And if there is, return the favor - let them vent. Be their shoulder. If they're notably quiet lately, it might be worth it to text them to see how they're doing.
They usually let you talk all you need. And the best thing you can do is do the same.