I am really sorry to hear this I read your post and had to reply as your situation is very similar to my own. My dad too was diagnosed with cancer and placed in remission in 2019 he had bladder cancer. However in December 2020 he was admitted to hospital with severe headaches and we found out that he has a grade 4 brain tumour. He has had his operation now to remove as much as can be taken without causing serious long term side effects but basically it will return as it is incurable. He has been given 18 months life expectancy. I am only 22 myself and habe now found my life turned completely upside down I have given up my job in order to move in with him and become his full time career. If you ever want to talk I am more than happy to help. Olivia 

The fact that you are only 18 is a tradgedy in itself. You're going to go through this. I am 45. My mum is slowly fading due to cancer and I don't know how to cope either. 
 

but you're not alone. I am one of four and we each have our own memories and relationship with our parents. So I guess you're the youngest like myself. 
 

I would say, you need to think about the moments you've had with dad and write them down. The holidays you have been, the way he used to tickle you, the way he adores you. 
 

trust me, I have an 18 year old and a 17 year old, and they are the best things to have happened in my life. You're dad will die better knowing that you are going to be strong, and do something good with your life. 
 

thys my advice - promise him you're going to live a dream life, be successful, and make sure you do all the things you want to do. 
 

he will rest easier knowing that you have thought about it.