@loneranger123
For me, it was about recognising that that grizzling, dissatisfied, angry, tantrum-ing child, was actually a part of me, now. Today. Every day. And about bridging the gap between the day to day 'adult' me, and the sporadic. triggered, 'tantrum' me.
I did it by recognising that when the inner me cries out for something (wants or doesn't want it), that's valid. I dropped any thought process that was similar to 'Is it just me?' or 'Am I just being silly, here?'... anything that was me internally judging my feelings. And recognising that feelings are different from actions.
I quite often see this mixed up on threads on here; 'My boyfriend looks at other women and I feel jealous - AIBU?', when the reality is, she hasn't actually done anything, so she can't have been unreasonable. Feelings aren't meant to be reasoned with! It would be different if she'd burned all his clothes as a result, but if she sat him down and calmly told him 'I feel upset when you look at other women', that's fine. So, the feelings are always valid, and how you present them to the world in your behaviours is the key.
This one recognition for me came in an instant, and I call it the moment when I grew up. I was 42! Now, when the inner me screams 'I HATE THIS!!!' I don't try to shut it up. It's fine to hate this, whatever it is. The internal dialogue used to be 'Stop being a stupid little kid. Why are you always so fucking angry?? This is what adults do, so just get the fuck on with it!' (leading to an explosion later) Now it's 'Yes, it's not really to your taste, is it. That's ok. We'll go home soon, and we'll get some chocolate on the way back: how does that sound?'
Your inner child, when it calms down, is actually what people refer to as your 'gut feeling'. It will guide you towards things you like, and away from things you don't like. It's the bit of you that recognises the nature of things, that senses things but can't quite put them into words. The bit of you that says things like 'I don't trust that guy. I don't know why, something just feels a bit off about him.'
You have to listen to and take care of those feelings. It doesn't have to be called 'working on your inner child'. Mine isn't a child, now, because I gave it the chance to grow out of having tantrums. It's a core voice. It's the real me that I always hid because I thought I should be different or better. You have to moderate your behaviour in response to the voice. Mine tells me it wants to buy a whole case of Green and Black chocolate and eat all of it NOW, quite often. 'Let's just have one bar for now...' will settle it down 
Once it clicked, for me, my life changed in an instant. It's not about relationships: that's just a symptom. It's about realising that I can do what I want, whenever I want. I can choose which people to be around, which events to attend, which hobbies to pursue, what to eat etc however I damn well please, and nobody can tell me I'm wrong. I can't choose to like things or people that I don't naturally like, so I need to choose carefully, otherwise I will spend my life putting up with things/people I don't like.
I hope that helps. It's a mindset thing. It's taking responsibility for yourself. Nothing at all has to change in your life to make this happen, because the change is in your head. And that means it can happen now, in a flash. Today, before breakfast, you can change your life massively for the better. I fully recommend it!