Allow me to give some background first. A friend of mine found a blog on the interwebs that had a short quote in there where they said that picking up your cross is also known as "sucking it up." (I'm not referencing the blog nor giving the exact quote for reasons that I hope will be made clear in this blog post).
I strongly disagree that sucking it up and taking up our cross is the same action.
Sucking it up implies that whoever is "sucking it up" is the one who is being the bigger man, who is doing the harder deed, who is making the sacrifice. It's their loss, they are the ones to be both pitied and honored at the same time. They're the ones who are putting up with an annoyance, dealing with a problem, or ignoring a troublemaking fool. It's about them.
When you tell someone else to "suck it up" (really though, can't you find a better way to say it?) you're telling them to grow up and stop complaining. You're instructions them to solve the issue or make it a non issue for them. The entire idea of "sucking it up" is self centered in nature - it's based around a human.
Which is entirely not what taking up our cross is about. When each Christian denies themselves, picks up their cross and follows God it is an outward expression of the inward recognition that we are in desperate need of God, we are sinners who are saved by grace through faith and this saving grace is not from ourselves. Rather it is God's gift, not by our deeds, so that no man may boast (my paraphrase of the Apostle Paul's words to the church in Ephesus). Taking up our cross is a denial of self, it is a death to self; when we take up our cross we die to sin, we are buried with Christ, and we live a life hoping and assured that God will raise us up from the death we are in through sin to life eternal with Christ Jesus our Lord.
There is nothing selfish about taking up our cross. Rather, it is the death of self that defines picking up our cross.
Now why would I call the selfish nature of "sucking it up" and the death of self through taking up our cross THE difference between the two? It comes down to how I define sin.
I define sin as choosing ourselves over God. The choice is not always directly made, but I think that all sin can be traced to a choice between ourselves and God. So when we equate dying to ourselves with "sucking it up" and getting over something by ourselves....I take issue. You can't both die to yourself and improve yourself at the same time. (I would argue that you can't improve yourself apart from God's grace but that's another topic for another time).
I realize that I just had a mini rant about what amounts to little more than a nuance of words, a selection of sounds and symbols that have no meaning apart from their context and the meaning attributed to them by speakers and listeners. Kinda makes this blog post look banal. At the same time, the words we say are important. After all, God reveals to us who He is through His words preserved for us in Scripture. It's worth thinking about the words we say before we say them.