Originally posted by AThousandYoung
I did develop. I developed all my pieces.
Developing your pieces is your initial plan. Once you've accomplished that, it's time to find a new plan. Try to find weaknesses in your opponent's camp, and make a plan to exploit them. Or find weaknesses in your own camp, and make a plan to mitigate them. Or try to figure out what your opponent's plan is, and make a plan to try to thwart it.
In the game you posted, look at the position after 11.Be4, which attacks the N on d5. If the N moves to f6 or e7, the pawn on e5 will get some unwanted attention via 12.Nc4. The pawn on e5 is currently a weakness in your position, so one plan might be to mitigate that weakness by controlling the c4 square. What moves help you accomplish that? I see 12...Nb6, contesting c4 directly, and 12...Be6 (13.Nc4 Nxc3), which is more subtle, and some others that don't help with the N being attacked on d5. Since the N is on a good square on d5, rather than move it, I would play 12...Be6. You ended up getting the B to e6 via Bg4, but looked more like an accident than a planned event 😉
Now look at the position after 13.a3. Why did white make that move? I suspect his plan is to play c4 and then b4, gaining space on the Q-side. So you could come up with a plan to counter that. Or you could decide that white's expansion on the Q-side doesn't bother you, and notice that white's pieces are starting to get cramped. This is a weakness in white's position, and a different plan might be to further reduce the mobility of the white pieces. In that case, 13...f5 is a fine move. But after 14.Bc2, 14...Qd7 doesn't help you accomplish your plan. Instead, consider 14...h6 to take away both Ng5 and Bh4 - keeping with the plan of restricting white's pieces.
Once you decide on a plan, look for moves that help you accomplish it. Of course your opponent will be making moves, too, so you need to constantly reevaluate and make sure your current plan still makes sense. Not all your plans will work, and many times you'll come up with a bad plan and lose, but even a bad plan is better than no plan.