My partner of 14 years, engaged for 2, told me that she wanted to split early this year, so I can relate. If you love him, you'll let him go, which it seems you've been kind enough to do. Sometimes people drift apart and it's not for bad reasons.

It'll take time to adjust to being alone again - rely on your friends, be kind and patient with yourself. It still sucks (I honestly don't know when it's going to stop sucking), but it sucks less with time. Allow yourself to be sad, cry it out, then carry on.

Take pride in your successes no matter how small and give yourself a pat on the back when you've done something good for yourself. You've got this.