I need advice quick.!

No. You are not wrong.

Make your decision. Talk it over. Be honest and direct. We have all ended relationships for all sorts of reasons. What you have expressed is a pretty common reason. It is not the end of the world.

My only advice is, don't drag it out. The quicker you get the break up over with, the better it is for everyone.

no. You never want to stop exploring the world. Ever.

He's not going to like it, & it will end badly. I've tried previously to tell him, but we just end up arguing. So that means, I will just have to be prepared for the outcome? You know. It's like I haven't been alone in 4 plus years. How will I manage?

Probably very well.

You will manage. You will not be "settling for something [you've] known since 17". Instead, you will be opening up opportunities to do the things you wanted: exploring new ideas, new experiences, new people, new relationships, etc.

No risk, no reward . . .

And frankly, would you want to stay in a relationship with someone who was "just settling" because he was too afraid of being alone?

Being alone isn't a bad thing; but in case you feel otherwise, being alone isn't nearly as bad as remaining in a stagnant relationship wherein neither of you is truly happy.

I remember the day I turned 21. I felt like everything had changed in my life, I wanted more, like you. I felt all grown up and there is / was so much out there to find out. I ended up with that "talk" and he was a gentleman, after 4 years together he let me go. I will always be grateful and respectful of him, he is the one I remember the most as far as boyfriends go. It was the best time of my life from there, I learnt to find myself totally and went on to changing my career path, gained a lot of friends or acquaintances I have this saying " if you love someone set them free, if they come back they're yours if they don't they never were"...

I also believe that every 4, 5 years we grow more. If someone remains content and as is yet we grow, then we grow out of that relationship.

4 years is a long time together, what ever happens from here, one day I hope you can be friends. Memories are just that and last forever.