It all depends on how you look at it.
So you have a glass. That's a given. I suppose the parallel here would be that you're alive. Certainly better than not having been created at all. I should point out that when Jesus says of Judas, at the Last Supper, that it was "good...for that man if he had never been born" (Mark 14:21) there's no point in arguing the facts. God decided to create me and here I am. You can certainly get into deep theological debate wondering the hows and whys of who is created for "honor" or "dishonor" (2 Timothy 2:20), but that's not our place. "Say not in thine heart, Who shall ascend into Heaven?" (Romans 10:6)
We need to focus on our own content and our own capacity. Though maybe not in that order, we'll see. Surely you've heard this:
"Is your glass half-empty? Or half-full?"
Now don't answer that just yet. Because by the time you're done reading this, you'll see that well-worn idiom in a different light.
"Be content with such things as ye have" (Hebrews 13:5). God is incredibly generous. Think of all the times (that's right all the times) that God expresses His abundance to us in His Word. Here's one for starters: "Verily I say unto you, there is no [one] (man or woman) that hath left house, or parents, or brethren, or [spouse] (husband/wife), or children, for the kingdom of God's sake, Who shall not receive manifold more in this present time, and in the world to come life everlasting." (Luke 18:29-30, emphasis mine) There's a lot to that passage, even things that might make you bristle and grimace, but the thing I want to focus on is the abundance that Jesus advertises as a reward for forsaking everything to follow Him. And before I go any further, this isn't a case for the simple acquisition for material wealth and possession.
When someone asks you, as I just did, whether or not your glass is half-empty or half-full, it would seem that the person asking is only concerned about the quantity of your allotment. Because it's still about how much you have, right? Only this time, the focus is on your perspective. And this is good, but there's a level deeper that we can go with this. Because "riches certainly make themselves wings; they fly away as an eagle toward heaven." (Proverbs 23:5)
Our possessions seem to be in a constant state of flux. Whether it's physical and material possessions to which we are referring or the immaterial things of joy, hope and happiness, everything we have is either wearing down, breaking down or replenishing in different states and capacities. Does this make sense? Do your shoes feel as new and cool as they did when you bought them? They may not or look new anymore, they might be just another old pair of shoes, of which you've had many. But I can guarantee you that if you're still wearing them, they feel better than they did when you bought them. Think about it. It's like you traded the transitory happiness of a new pair of shoes for the lasting contentment of a favored pair of sneakers. Ah! "How beautiful are the feet that preach the gospel of peace, and bring glad tidings of good things!" (Romans 10:15) I say all of that to remind you to focus on the basis for which we all live. Namely, the fact that we were created in the first place, created for a purpose. So rewinding to the original question, if I ask you whether or not your glass is either half-empty or full, don't answer until you're grateful that you have a glass to begin with.
Here's another way of looking at it. Take what you have right now and--follow me here--pour it into a smaller glass. "Humble yourselves therefore under the mighty hand of God..." (1 Peter 5:6) Because if you see yourself (your glass) as smaller than it is (not self-pity, humility), and your possessions or allotment with gratitude, then your glass will, by default, always be full. "And to know the love of Christ, which passeth knowledge, that ye might be filled with all the fulness of God." (Ephesians 3:19, emphasis mine) By the way, don't concern yourself with others' perceptions and opinions: "I am small and despised: yet do I not forget Thy precepts." (Psalm 119:141)
"For ye know the grace of our Lord Jesus Christ, that, though He was rich, yet for your sakes He became poor, that ye through His poverty might be rich." (2 Corinthians 8:9)
There's another side to this though. Look at Psalm 23 (verse 5):"my cup runneth over". David is saying here that he has more than enough. If you have enough to live comfortably, and can therefore give charitably, then by all means, please do so. "...For a man's life consisteth not in the abundance of the things which he possesseth." (Luke 12:15)
In closing, take a look at this verse from 1 Kings (17:14) "For thus saith the Lord God of Israel, the barrel of meal shall not waste (run out), neither shall the cruse of oil fail"—uh, run out? Nope, listen: "until the day that the Lord sendeth rain upon the earth." This verse is talking about Elijah and the time he stayed at a woman's house during a severe drought and famine. The woman had determined to use up the remaining flour and oil she had to make a last supper for her and her son--and then die. When the prophet Elijah heard that, he asked that she make him a little something first. She complied and fed the prophet and so God rewarded her with a neverending supply until He came through with rain.
"Pressed down, and shaken together, and running over" (Luke 6:38)