Today is not yesterday, nor is it tomorrow. What it means to me is that whatever the problems that we face today, must be faced today without looking at the past, or hoping for the future.
Let me give you an example, I am a lecturer. Now I regret being one, not due to the students but some other factors. I would never blame you all for what happens. Looking in the past would mean regretting my past decisions like why did I quit being an engineer? or why did I not follow my friend when he went for an interview at a company (he's like a manager now). There is no point regretting the past, and I am blessed to meet you all because of my job.
Hoping for the future means that, well I'll do my Phd, then I'll apply to USM to be a lecturer there. Remember the current situation is now and you need to survive the current situation to dream of a better future. So be realistic in analysing current situation.
So have a nice day today.