Eleanor Roosevelt was the first to gain widespread recognition for this quote, though the double entendre is so obvious, she can't have been the first to notice it.
"Yesterday is history, tomorrow is a mystery, and today is a gift; that's why they call it the present." (emphasis mine)
So, for purposes such as these, forget yesterday and forget tomorrow. Let's dwell on the present. Retaining the concept of gifts and presents and whatnot because, let's face it: "every man is a friend to him that giveth gifts." (Proverbs 19:6)
But until we learn to see that each day is a gift and that every opportunity and every problem contained therein, are gifts (how else can I say it), then we'll be miserable and the grass will always look greener. And if you're fine, and things are cool and you already know this stuff—because these topics have been bandied about incessantly—then feel free to go about your business. If you're still reading, I'd like to present these matters in a different refraction.
Problems are gifts
Any worry that we feel arising from the problem—our perception of it—really has nothing to do with the outcome of what you're facing. God asks Adam and Eve: "Who told thee that thou wast naked?" (Genesis 3:11) In other words, God's asking "who told you that I wasn't enough?" What (or who) tells us that the worry that we infer and perceive is true? Sure, circumstances might look less-than-promising, but, "we walk by faith, not by sight." (2 Corinthians 5:7). And learning to see a problem, not as the end, not as something tailor made for our misery and downfall, but as a blessing and an opportunity and as a gift is worth more than all the problems you could face. Does this make sense?
One of the chief causes of despondency and fist-shaking at God, is thinking and seeing that the things we face that seem so insurmountable, are just that. Insurmountable. How many of us have turned back from the simple childlike effectiveness of our youth in Christ because we encountered a conundrum that didn't make sense in light of what we'd found, namely eternity?
"We are troubled on every side, yet not distressed; we are perplexed, but not in despair;" (2 Corinthians 4:8)
Is it right to say that the more problems we have the better it is? Granted, much of life's perplexities weren't our fault. But we find ourselves stuck in the middle of a particularly persistent and vexing issue and what do we do? All we do is wish it gone. Let me tell you that the hard task with which you've been blessed to partake in is the springboard to your future doing the things that you want to do for God. And nothing short of digging in and staying for the duration is going bring about the solution. Well, that and learning to wait on the Lord and know and love Him through it. Paul dealt with these troubles and perplexities correctly because God showed him how to look at them.
"Many are the afflictions of the righteous: but the Lord delivereth him out of them all." (Psalm 34:19)
"The eyes of the Lord are upon the righteous, and His ears are open unto their cry." (Psalm 34:15)
"For He hath made Him to be sin for us, who knew no sin; that we might be made the righteousness of God in Him." (2 Corinthians 5:21)
Everything's a gift
It's Gospel. Talk to anyone who's made it in any field or endeavor and they'll tell you: The problems they encountered on their way to the top were what made them. The good times? They come and go. Don't become a masochist, enjoying pain for its own sake. But welcome each and every misery as a gift. It'll get God's attention when you do this. And He'll have no choice but to bless you (but hasn't He already?). The fires of struggle will burn out any impurities and you'll come forth a new person. With gems of knowledge and understanding that you wouldn't have been able to learn any other way.
"And He said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me. Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ's sake: for when I am weak, then am I strong. I am become a fool in glorying..." (2 Corinthians 2:9-11)
That's the thing about any problem you face. It's a gift because we get the privelege of experiencing a measure of what Jesus went through.
"Ye are my friends..." (John 15:4)