I find that if I stay organised, and by that I mean:
1. I have plenty of stationery (stamped addressed envelopes with payment instructions, etc).
2. I finish work, fill up the van and get ready for the next day.
3. My window cleaning data base is upto date.
4. My work list for the next day is produced and all phone calls/texts (for access) is made.
5. I have stuff in the house for lunch.
6. I have something ready for listening too on my MP3 player.
7. Any invoices I have to e-mail are done.
That going out to actually clean windows isn't such a chore.
But if I let things go, don't update my database, don't stay on top of my invoicing (I have a bad habit of cleaning and forgetting to invoice), don't have stationery handy, there's nothing on my mp3 player ready; that getting out to work becomes much more difficult.