The way I deal with it is putting 10% of my portfolio in 9 different index funds (IGOV, VDE, VBR, VEU, TIP, VNQ, VWO, EFV, VTI gets 20% allocation).
This way, while it's probably not going to give the best returns, whenever I am adding money and rebalancing (i never sell, i just add money to make it as balanced as possible so i don't incur a tax hit on my non-tax advantaged accounts), it makes me feel like I'm always buying more of the laggard and helps to keep me on track and not shifting strategies.
It's probably better for long term gains to just junk everything in VTI, but I don't think I could do that mentally. I feel like more of a winner with my 9 fund balanced approach. It's not logical but it works for me.
So, right now, international (like VEU) hasn't been performing very well and other funds have, so I'll by less of those and more of VEU and feel good about it. You can follow a similar approach. It's never doomsday everywhere! :)