Think positive, think positive, think positive . . . Christianity is not a series of "happy thoughts". It's important to keep our minds active and positive, yes, because life is not a cakewalk. It's one step above Hell, and that's it. That's why we have to think positive; not so life will be better, but so we can alter our perception to accept the good with greater joy, and meet trials more graciously. Unless i'm mistaken (and that is likely), Paul was the one who wrote about thinking of things that are good, to keep our thoughts on the joys in life . . . The same Paul that was haunted by his past as a murderer of Christians, and he was imprisoned much of his life for sharing the gospel . . . What good did thinking of positive things avail him? Well, it certainly didn't make life easier, just easier to bear.
In fact, he had a "thorn" in his side that Jesus wouldn't remove; "So to keep me from becoming conceited because of the surpassing greatness of the revelations, a thorn was given me in the flesh, a messenger of Satan to harass me, to keep me from becoming conceited. Three times I pleaded with the Lord about this, that it should leave me. But he said to me, “My grace is sufficient for you, for my power is made perfect in weakness.” Therefore I will boast all the more gladly of my weaknesses, so that the power of Christ may rest upon me. For the sake of Christ, then, I am content with weaknesses, insults, hardships, persecutions, and calamities. For when I am weak, then I am strong."
To be a Christian in our demeanor regarding our outlook on life isn't to walk around with a fake smile on your face, saying "Everything's okay" every day, no matter what's going on. It's not stubbing your toe and laughing instead of saying "Ouch!" It's not grinning when the doctor informs you of bad news.
It's saying, with thanksgiving (Eph. 4:6) "God, the circumstances are tough, i can't always handle this alone, and sometimes life is simply coming apart at the seams, but i know Your grace is sufficient; Your grace covers me; Your love, patience, wisdom and power are emphasized by the trials i face, so i will face them knowing You are with me."
So yes, think positive, but don't expect it to make life easier or for blessings to pour into your life because of it. If Satan isn't attacking you while he can (which is in this life, or in Hell; he can't touch us in Heaven so he will attack the elect as much as he can while he can), something's not right. If he's not testing you, test yourself to make sure you're saying what needs to be said, doing what needs to be done, and fighting the battles that need to be fought.