The first place we lose the battle is in our own thinking. If you think it's permanent then it's permanent. If you think you've reached your limits then you have. If you think you'll never get well then you won't. You have to change your thinking. You need to see everything that's holding you back, every obstacle, every limitation as only temporary.
"The mind is everything. What you think you become." Buddha
It's so amazing to think of the control you have over everything! It is up to you how you feel every single day, how you react to different situations, whether you can control them or not, everything you do or say.
You wake up tomorrow and it is pouring rain, no matter how inconvenient you may feel that is, it is your choice how to handle it. You can be frustrated or you can just decide to be happy and go jump in the puddles.
And on a more serious note, you have an appointment with the doctor, and you are afraid of the diagnosis, you have a choice about how you react. If you are scared to death it is a choice and if you can choose to be scared, you can choose not to be.
If you think you aren't good enough, then you aren't and never will be until you change your thinking. You are the only one that can change it, nobody can tell you that you are enough or try to talk you into believing it, it is up to you. It is your mind telling you these things and you can change your mind. Don't listen to anything negative, from anyone and especially not from you. Fill your head with kindness, love, health, wealth and goodwill and it will be yours.