How does one continue living when nothing is enjoyable and there is nothing to look forward to?

Seek help ASAP. You are describing 2 of the main symptoms of major depression: anhedonia (loss of interest) and hopelessness. These and other symptoms of depression respond to treatment, including talk therapy and medication. When you start questioning the reasons to live ( suicidal ideation) then you need to seek help as soon as possible, perhaps starting with your primary care provider.
Work to change that. It sounds like significant depression has colored everything gray in your life. Don't believe your feelings, do something about them. Get active living your life and work on changing your outlook. Nothing is more important than doing things to help lift your spirits and be more positive. Have you considered counseling or medication? Treat your depression, joy will come. Your outlook will change.