Yes, I also finished this recently. I keep thinking about it and have managed to apply the 'just let it go' thing a few times. It really helps me reset my mood and stop overthinking stuff. Paraphrasing part of the book I think Singer writes something like 'if you apply this method then you'll truly have no problems for the rest of your life' and I think as crazy as that sounds, he's not wrong. Doesn't make it easy, but as he puts it, 'opening my heart' definitely works for me.
I may be more receptive than some to this kind of advice (due to exposure and a lot of what I consider personal growth—I used to be much more Cartesian in my thinking), but I'd recommend the book to most people regardless.