The best way I find is to be super organised and have a plan for each week. Sounds nuts but I am speaking to fellow horse mad folk right now so I assume I'm in good company. I have a weekly plan for each horse where I can fit my riding around work / non-horsey life.
The clocks go back soon, which leaves even less light and means riding early before work and on lunch. I am lucky that my horses are super close which makes riding at lunch do-able (10 mins drive / 10 mins tack up / 40 mins ride) and they live out so I can pooh pick pretty much whenever I have 30 mins free and my lovely yard managers feed for me in the morning or evenings depending on which end of the day I will be there - this really helps.
When I plan my week I factor in my sharer who rides on set days on one of them, then the other two who are in full work a minimum of 5 days per week each, its tricky but it can be done. One horse is ridden in the morning before work and one is ridden at lunch 3 days in the week, I will ride and lead twice in the week also which gets two out at once for hacking. The weekends are usually hectic with at least one day hunting/competing then the other day riding at least two.
So, it can be done but it does mean you have no other life than your horses and your boyfriend may try to strangle you in your sleep, but other than that its happy days- for the 'horse mad' its perfect, but for those who are less keen, it looks like I have finally lost it !!