Truth is when you focus on what you are yet to achieve and the hurdles to your achieving them too much, you will be discouraged and may stop the journey altogether. Overthinking is not good and like you said can cause a lot of health issues and even making one make a wrong decision that may cost one so much in life.

Sometimes when things aren't going the way you desire, it's okay to take a break, look at it and try to figure out what you are doing wrong or what you are not doing at all.

We do not have power over the future, the past is gone and what we have now is the present. Do the best you can and leave the rest. Eventually, everything will sort itself out.