To strain, or to strain yourself, is to try very hard to do something, or even to hurt yourself while trying to do something. For example, to strain your eyes is to try very hard to see something that's hard to see.
Straining doesn't have to be something you do with your body; you can do it with your mind. I would have to strain myself to multiply two four-digit numbers in my head; that means I would have to think very hard to do it. It would be a struggle. You would have to strain yourself to play three sports, take weekly piano and violin lessons, and see two tutors every week for advancement in math and writing, all on top of all your regular schoolwork and chores. Please don't strain yourself like that!
Difficult situations can place a strain on you, or place a strain on your family or your friendships. That means that difficult situations put too much pressure on you, and make it too hard for you to do what you need to do.
For example, if you live in an apartment with very noisy neighbors all around you who blast loud music 24/7, they're putting a strain on you, and your family, and your studies. You'd be trying to do your homework, but the loud music would keep breaking your focus, until you shout, "I can't take the strain of this noisy apartment anymore!"
The word "strain" has many more meanings—you can strain your pasta, meaning you remove the water from it, or talk about a strain of a virus, meaning a specific type of that virus—but much of the time, to strain to do something is to try very hard to do it.
Make a flash card:
You can write your own definition and choose your own picture, or copy mine.
to work very hard to do something difficult
Write your own sentence!
You can use either of the two ideas I'll suggest, or you can invent your own. Include as much detail as you can!