How does someone overcome guilt and letting go?

Good afternoon and thank you for your inquiry.  It sounds like you have been through a lot with your father, which has led to a very complicated relationship, to say the least.  I am glad that you are reaching out now to help yourself heal and to move forward.  Have you ever sought counseling before?  While you didn't go into detail about your childhood experience, it sounds like there is a lot that needs to be processed first and foremost.  True, it might bring up some very raw and painful emotions, but will be an integral part of your healing journey. 

Every therapist has their own unique process when working with clients and from what you wrote, it sounds like a lot of the work to address your goal of overcoming your guilt and letting go will not only focus on working through the experiences that you went through, but also providing you with tools to be better equipped to cope with the relationship you have with your father.  Having someone in your life who is diagnosed with bi-polar disorder as well as substance abuse issues takes a huge toll on not only their own lives, but also the lives of the people with whom they are close. 

In addition to giving you the space to process everything, there are also some valuable tools you can learn when interacting with someone who has mental health and substance abuse issues.  Psychoeducation - can really help you better understand any mental health condition, which I think can be crucial for you on your journey.  This, coupled with learning strategies that you can employ to help the situation not feel as "mentally draining" will be key.  This could be where learning different mindfulness techniques and working to change your thought process could be very beneficial.  Both of which could be explored more in-depth with your therapist.  As I insinuated earlier, it is important to note that all therapists have their own orientation and could teach you other tools that are equally as beneficial.  To give you an idea, the website www.therapistaid.com has some really good resources that I would recommend taking a look at.  

The other thing to really focus on is what does your support system look like?  It can feel very lonely when you don't have people to whom you can turn.  In addition to friends and family, have you ever tried any support groups, like Adult Children of Alcoholics & Dysfunctional Families? - https://adultchildren.org I'm sure there are others too out there. 

To summarize, in seeing that you feel stuck in finding the time to get the help, I think that the BetterHelp platform is a good starting point for you.  Online therapy does make the first step of "showing up" easier.  There is also no set timeline for when you can say "okay, I've let go and don't feel guilty anymore" and I think it is important to keep in mind while on this journey so as to not get discouraged if it doesn't seem like it's happening fast enough.  Good luck and I hope you're able to find the support that you are looking for.