So, you have decided to have 2 separate accounts for work and personal.
Here are steps to follow to use both git configurations simultaneously with the same .git-credentials.

Step 1: Separate Work/Personal directories

Create a work and a personsal directory in your Documents folder. Use these directories to separate your git directories.

  Documents
  ├── work
  │   ├── ...
  │   └── ...
  └── personal
      ├── ...
      └── ...

Step 2: Separate git config for each account

• Create .gitconfig-personal in the personal dir.

  [credential]
    helper = store
  [user]
    name = Personal_Username
    email = personal_email@domain.com
  [credential "https://github.com"]
    username = Personal_Username
    helper = store

• Create .gitconfig-work in the work dir.

  [credential]
    helper = store
  [user]
    name = Work_Username
    email = work_email@domain.com
  [credential "https://github.com"]
    username = Work_Username
    helper = store

Step 3: Update global .gitconfig to switch the profile based on directory

• Update your global config using the following command.

  git config --global --edit

• Add the following config.

  [includeIf "gitdir:~/Documents/work/"]
      path = ~/Documents/work/.gitconfig-work
  [includeIf "gitdir:~/Documents/personal/"]
      path = ~/Documents/personal/.gitconfig-personal

Step 4: Register Access Tokens

• Check your .git-credentials file & add GitHub access tokens for each account.

  https://Personal_Username:PERSONAL_TOKEN@github.com
  https://Work_Username:WORK_TOKEN@github.com

That's it, the next time you pull/push/clone a private repo, git will automatically choose the correct token for each config.