payment...it's part of doing a job

This is just a little rant. I don't feel like saying it out loud to someone so I will just write it here. I think sometimes just getting it out can make me feel better.
I hate to ask for money. I think most people feel the same way. When I started my business 3 years ago, I was very clear what my hourly wage was, $65 hr., the minimum time work, 3 hours and payment must be made at the end of each organizing session. I had worked for a previous employer who getting a check out of her was next to impossible. Well whenever I break one of my payment rules, you can guarantee that there is a problem. I have even had a client just not pay me at all!
Recent scenario...met with couple who moved into apartment and need help setting it up and organizing it to feel home. There were many tasks that needed to be done and some even before I came for my organizing day. I researched best solution items, went and bought those items and in one case had to build a shelving unit. So before I even came for my first appointment I was out time, labor and cost of expenses. Organizing day comes and I bring an assistant in to help with the job. Being a responsible employer I have my check book with me and pay her immediately. Now I am even deeper in the hole. No problem, I will get my check at the end of the session for everything. Client came home, loved what we did and I get the old version of the check is in the mail... "my boyfriend has the check book can I pay you tonight via PayPal". It is now two days later and no payment has been made. There have been a couple exchanges of emails - "I got your invoice and will pay it tonight." "Does the invoice include the discount you mentioned at our first meeting". I have tried to be polite and even took off the time I spent prior to my organizing session - roughly $365.00 and...still no payment. . In my gut I know I will get paid but the interim time of this...SUCKS. I keep looking at my email waiting for that notice from PayPal that I have received a payment. I even have gone directly to the PayPal site with the excuse that maybe their notification system is down. Nothing.
48 years old and I am still learning things the hard way...Session is done and you pay me now.
To keep my sanity today I need to make a deal with myself...I will look at my email only one more time today and fingers crossed that payment comes in by tonight.Deal? Deal.
Please send me my money. Thank you.