You say: I can't go on!

You are at a point, where you feel so drained and tired and frustrated and helpless, you don't know how to continue. Oh what a terrible situation to be in!
I've been there, too. And I know, when you are in that situation, it is difficult to find hope. However, if you can, please believe me, life can turn around again, and you can be happy again!
Not always, but sometimes, our decisions are the reasons for the circumstances we find ourselves in. If this is the case, the only way we can ever get out of our misery, is to start changing what we are doing and believing. Once we change our approach, our priorities, things have to change.
All too often, we think what we are doing is the “right thing”. That we have “no choice”. If this is what you are thinking, it is an indication that you are not open minded! There is always a choice! There is no such thing as “the right thing” or “the wrong thing”. Every decision we make has consequences. Every option causes different outcomes. If you don't like where you are right now, the first step I would recommend is to identify the options that are available to you.
You could apply the principle of brainstorming: just throw up anything that comes to mind – even if it is totally unrealistic, or far-fetched. We often do not allow ourselves to look at other options, because we discard them before really thinking about them. Our priorities, our wants, our belief-system causes us to discard valid options, without really looking at them.
For example: if you live in the US and you are not locked up and able to walk, there is always an option to just get up, leave the house, get on a plain, or a freight train, and go somewhere else. You may not allow yourself to see this as a valid option, but it is.
Another example: you can always quit your job. Maybe it is difficult to get a new one, maybe you'd have to move, maybe you couldn't pay your mortgage. But you can quit your job!
Naturally, some of the options would require us to think about other areas in our life: if I am suffering in my job, and I feel I can't quit, it is not that I am disallowed to quit the job; it is, that I don't want to change certain other things in my life, where the status quo requires me to stay in my job. Once I see quitting my job as a valid option, I can make the next step, and examine what changes I would have to make in other aspect of my life. Now I am a step further. Can choose to sell my big house and get a less expensive home. I can switch my car to a scooter and reduce my transportation costs dramatically. I can move to a less expensive area. Suddenly I see many options!
So, when you say, you can't go on, I can only recommend to look at all the options you have – and there are many. Maybe, you are focusing on the wrong things, and the Universe is trying to block the path you're trying to walk, so you look around and walk a path that will lead you to happiness and fulfillment.

The Universe needs you to help improve the situations in this world. You have a mission, and the Universe supports you in this mission. If you can find your mission, and align yourself with it, every cross gets easier to carry, every situation gets easier to bare.