Never Park in Insert Mode

Vim is set up to do more navigating than editing. It rewards you for working in the same way, mostly in control mode with spurts of time in an insert mode.
If you try to use vim as a weak form of notepad, modality and navigation will ensure that you are never really efficient. If you want to sail, you have to get in the boat, and if you want to get good at vim, you need to get good in command mode.
So, if you are stopping to think, hit <esc>. If you aren't in the middle of text typing, you should be in command mode. If you are wanting to move up or down a line, or to some other place, hit <esc>. If you walk away from the keyboard, hit <esc>. Otherwise, you will start to type commands and find that you're not in command mode and you have lost your ability to meaningfully use . or undo.