Life only presents you with challenges you're capable of, or whatever. Somehow, I don't feel capable enough for this.
I feel like that statement is nonsense. Who said that? Is that a direct quote? Sounds like something you'd see on a guidance counselors bulletin board. It's as ridiculous as "god won't give you more than you can handle". Inguess first we need to define the expectations of what is to be understood by the word "handle" in this context.
I feel like we cling to phrases we make up that set us up for failure, sometimes.
My therapist told me something like that yesterday 
"You're only going through this because you're tough enough to handle it"
Right?! Like wtfff does this mean? Haha
At any rate, he said this because I recently have had thoughts of suicide (or at least self-harm) on the back of depression from being rejected from my job, and anxiety about an uncertain future .
And he told me that a higher power is having me experience this so that I can prove to myself how strong I actually am.
Which in turn made me feel even weaker , or at least not my best stuff