The biggest issue that will affect your peace of mind is whether or not you have a financial cushion. Can you survive for a month or two on a significant reduction in income? If the answer is no, then you might need to suck it up and accept some jobs you might not normally take. This means taking on projects that pay less than you normally receive, that are not as satisfying as your regular projects, or (in my case) taking on projects that are longer and reduce your flexibility to accept more interesting or lucrative projects. You still have to pay the bills, right?
If you do have a cushion, then your options expand a little bit. Can you relax and give yourself a mini staycation? You could binge watch a TV show or enjoy a little more time with friends and family. But you can't totally relax or that mini vacay may last a little longer than you expected. You have to keep in touch with your clients and remind them that you are available if they need anything. If you have a strong relationship with your clients, they should be happy to hear from you and won't bristle when you ask if there are any projects coming up that you can help with. They might say no but it never hurts to ask once or twice a year during the slow periods.
Don't let your down times get you down (come on, you knew that line was coming). If you are able to save enough of a financial cushion to keep the lights on during your slow periods, you can actually enjoy them and maybe even use the free time to start something you wouldn't normally have time for, like a blog post.