St. Paul asked a few times to have a “cross” removed, and consistently got the answer “My grace is sufficient for you”.
A cross is one of those nagging things that you struggle with. Leads to envy and other things if you let it (why did xxxxxxxxx have to happen to me?). Yet, we are instructed to carry, bear, or otherwise deal with that cross and follow Christ.
It is a burden put on us to keep us “honest”, that is, following Christ rather than ourselves.
What is a cross to one person may not affect another person to the same degree or even at all. We each have our own crosses unique to us.
Sometimes we overcome these burdens, finding in the end we are closer to Christ, a better person, and the cross isn’t there any more.
Sometimes they come and go.
Some struggles are lifelong.
My observation is that universally, these crosses tend to help us focus away from ME ME ME, and more towards our Loving Lord.