Do you even lift, bro?!
Sorry, I jest
Either moving on with someone else is 'too soon' for you, or you just have to step up and get on with it.
Don't waste your time looking back, or wishing over the future. NOW is what matters.
I believe I've said this before in this topic, but in order to escape your past you need to alter your present circumstances - change
up your life, see new people (you're doing that already - at least to some extent), get a new hobby/interest, start getting fit - no, really... start doing exercise, wight training etc. Something,
anything to get you away from what you were before, something that has you
moving forwards so you are not left standing still wondering wft just happened

I cannot stress how important the need to keep moving and not have your life come to a standstill is.
When you step back from this sort of advice, you'll see that amongst being reasonably sound and common sense, it reflects a kind of CBT (cognitive behavioral therapy), in that you are altering patterns of thinking and learned behavior. The main difference between common sense advice and 'professional help' is that the first relies on your own sense of discipline to enforce your actions.
You need to stop expecting to fail. Because if that's what you expect to happen, than that's exactly what will happen, because
you have made it so with your expectation.
Of course this doesn't mean that the most positive outlook in the world will prevent things from going south. But it does mean that your attitude to the events is able to overcome and keep moving, regardless of the perceived emotional strain you experience.
Now that all sounds complicated and stuff. But it really isn't. After all, you don't complete a marathon in one giant leap, it's a whole
****load of little steps with the most important factor being that no matter what, you keep putting one foot in front of the other.
Don't dwell on what you cannot change. I've been there before after braking up a long term thing (nearly 10 years? fyi I was on the receiving end of the breakup). It knocks you about but you have to keep moving and things like confidence and hope and all of that good happy stuff will sneak back in when you're not looking because you're too busy getting
**** done to notice.
I'm sure there's plenty of others here who will say the same.