Conserve Your Power Armor & Find a Place to Store It
Unlike Fallout 3, you'll gain access to Power Armor very early on in the game. I've spent a ton of time upgrading the power armor but I've also spent a ton of time outside of the hulking armor. Fusion cores aren't a dime a dozen early on.
In Fallout 4, you need fusion cores to fully power your armor. And they aren't exactly easy to find in the early part of the game. So, you'll want to be strategic with how you use the armor. Save it for when you really, truly need it.
The nice thing is that you can leave it, come back, and it's still there. I've gotten into a habit of leaving it near my go-to workbenches so that I can easily modify it when I return with an inventory full of loot.