Can you change your life by changing your core beliefs? Can you even change your core beliefs really?

I have been doing a lot of research  on core beliefs. See, we all have em'. The programming we use everyday to make decisions,get things done,achieve our goals and dreams. The rules to our current (and ever changing) identity. 

Sometimes they hold us back. Sometimes they are pretty obvious (I hate math) and some are more subtle ( I am afraid of rejection,therefore I am  bit of a perfectionist)

I have been through a bit of mental health treatment. I know I have the belief that "I am not good enough" which regularly rears it's head in ways I thought were just my lack of discipline. 

Yesterday on Instagram I found a post 

https://www.instagram.com/p/CkSdqWgJGZO/?igshid=YmMyMTA2M2Y=

How to uncover your subconscious blocks. 

I mean, yeah. This. Why have I kept missing ballet class? Why do I have epicondylitis again (limiting my lifting and fitness goals).

Do I really have to start identifying as someone who "never misses 2 workouts in a row?" (Not a terrible idea) . Or someone who "loves protein and veg?"( also not a terrible idea). 

Or could it be......I believe deep down that I am not good enough for what I want/success and therefore also, am unlovable (demonstrably not true) and to go against this core belief would mean I had spent years of my life just holding myself back? 

I mean,kind of. Yeah. 

And thats ok to mourn,also,how do I full rewrite this belief?  

Can I rewrite it by drowning my mind in positive affirmations everyday and all night? Personally researched,written and recorded by me? Will this work?????

Fuck,I hope so. Tired of holding myself back. 

So,what does success mean for me?

-Officially replacing caffeinated coffee with decaf. ( intermittently successful)

-Grow my muscles into a body fat percentage of 22%.

-no more fucking injuries every 2 months. 

-relaxing  confidently into my growth