How do I assure myself tonight that tomorrow I will do the things

You can't assure yourself the night before, unless you uber motivate yourself before going to sleep in order to wake up early. You have to actually start it the night before or you never will. This is a "do what i say, don't do what i do" deal cuz i failed hard like 2 to 3 weeks ago.

Just do it one day at a time

make a list of things you want to do
do and cross out at least one of the things daily until the list is done

pro-tip: the list is never done