Desperado: You have not wasted or lost anything. All along your path you met relatives, friends, acquaintances, classmates, etc. Everyone you ever met has been influenced by your presence. You have left your footprint in their lives. And they are better for it. You have contributed to their benefit. And they have contributed to you. Feeling that your youth is gone at 25? You have only traveled inches...you have miles upon miles to go. And if you have cancer, we have taken great strides in treatments and even cures for it. The Cancer Treatment Center does not advertise because of failing and failures. They would be a great lace to start.
Your sense of loss and despondency is most likely your negative epiphany. And you feel negatively. I am a Christian. And several things are facts: God, or the uinverse if that works for you, wanted you enough to make you, Loves you enough to save you, and is faithful and true enough to keep you safe. Hell shall not prevail against God’s ekklesia. Google it.
As far as being at the end of your....whatever. False assumption. You can start doing right now those things you feel you missed out on. If you always wanted that He-Man doll, you can get one today. If you always wanted to find love, google singles groups would n your area and meet other people. Christian singles. Parents without Partners. Both have people who personally know other groups of like purposes.
If you have cancer, google Cancer Support Groups in your area, and connect with them. People with like minds/situations/illnesses are a repertoire of valuable ideas, contacts, information and support, among other things.
You are not even close to the end. Your positive epiphany is overshadowed with negativity. You actually have realized that you need to get out and do stuff that is fun and gives meaning to your 1000 year lifespan. Google Advances In Longevity.
Do not be deceived, God is in control.