I've been down that road you are talking about and found that breaking promises that I made to myself was due to the fact that I really did not need to do what I promised myself to do.
Like you I put the pressure of guilt on myself for nothing because when the time come that I really needed to do something because of certain factors due to ones responsibilities in life there were no need of promises I just did what I had to do.
During ones life we are inundated with many problems, many that do not concern us as individuals yet we for some unknown reason get involved because of what MIGHT happen.
Well I've learnt to ignore such occurances and deal with what actually involves myself and if need be, act upon it automatically.
That way one learns to be proactive and not be caught up with the jungle caused by outside circumstances or other peoples fears.
Live your life with as much freedom as you can get find, promises are traps we should avoid when like you say,
"Just Do It".