The best way is to look at the symptoms you're experiencing
How to know it's the right time? For me, the best way of finding out is to look at the symptoms that you are experiencing. Maybe you are feeling overwhelmed. Maybe the things that you've been trying to do are not working as well as they used to. Maybe your results aren't as good as you hope they would be or perhaps as good as they were for and you can't think why that it's happening. Possibly, you are feeling frustrated. There might be symptoms of anxiety or a lack of success in your perceived efforts. And the other things is perhaps that you haven't got any motivation or you think that you can't be bothered to go and do things that you won't choose to really enjoy doing.