Gratitude. That is the answer you seek for being happy in the present, while still striving towards improvement. Instead of focusing on the things you're "missing" focus on what you have and be thankful - including gratitude for the desire and opportunities to grow and improve.

Start with a small, simple gratitude list each morning. Three things, minimum. Five is better. Ten if you're feeling ambitious. But it's more about the mindset than the number of things. Once you get the hang of it, things snowball and you quickly lose track of the number.

For example: I hate folding laundry. I was pissed off the other day when I realized I had a clean pile sitting on my bed that I needed to deal with before bed. Instead of ruminating on how much that sucked, I shifted perspective to be THANKFUL for all the privileges and conveniences and good fortune that having clean clothes to fold entails:

I have clothes to wear! Not just what's on my back, but lots of clothes. Different outfits for different occasions, suited to different weather, different purposes, etc. I have decent furniture and a small walk in closet to put my clean clothes in. I have a washer and dryer in my home to clean my clothes at my convenience, rather than going to a laundromat. I have clean running water to run the washer. I can afford the electricity to run those machines. Hey, that means I have a steady job to be grateful for...and it goes from there.

Maybe this example doesn't apply to you, and some people frown on it with the attitude that it's like saying, "it could always be worse" - and I guess it is to some extent. But it's more like opposite sides of the same coin because you're grateful that it isn't worse and finding joy in that simplicity.

Hope that helps, even if I've explained poorly.