It's not always like the picture above. Flat water makes casting easy, but wind is often a good thing. People often hate fly fishing in the wind, but to be a well-rounded fly angler you need to learn to effectively cast and fish through it.
Despite the challenges a stiff breeze presents, it can make the fishing downright dynamite, too. The ability to cast properly will likely be at the forefront of most peoples' minds on blustery days, but there are some techniques you can use to make presenting your fly less frustrating. Casting in a strong wind might not always be pretty, but it's often doable with some tweaks!
Tips for casting in the wind:
Change Position: The simplest thing to do is change the angle of your cast. If the wind is blowing directly into the bank you're casting from, try quartering your casts to the left or right a bit so that you're not throwing straight into the wind. The more angle you can put on the cast in relation to the wind direction, the easier casting becomes—relatively speaking, of course. I've fly casted in 50+ mph gusts which didn't make for the most stellar presentations, but by putting some angle on my casts I was at least able to keep fishing long after literally everyone else had left...and the fishing was insane!
Another note about changing angles is to try and keep the wind direction blowing onto your non-casting side. So, since I'm right handed, I'd want the wind to be blowing onto my left side. This way, when I'm casting the line will be blown away from me rather than into me, which can obviously make casting both difficult and hazardous.
Line Speed/Double Haul: Wind is like a giant barrier that needs to be sliced through. Everyone should be comfortable with performing a double-haul cast—windy or not! It's a necessary skill. Casting with high line speed and a tight loop keeps the line profile fast and compact which cuts through wind effectively. One caveat to this is that casting very heavy flies or awkward rigs often requires a more open casting loop or something like a belgian cast (read about that here) to get the flies out there properly and safely, but when it's very windy switching to a leader/fly setup that's easier to cast might be a good idea.
Rod Angle: Casting with the rod angled more out to the side to some degree is a great tactic to use. Using this "sidearm" style keeps the line/fly lower throughout the cast which has 3 benefits: there's less wind the closer to the ground you get, the fly and line can touch down onto the water's surface faster when the cast completes, and it's a good way to keep the fly further away from your body/face so you don't get an unwanted piercing. You can even extend your arm waaayy out while casting sidearm to keep the line even further away from you if necessary. Again, not textbook or pretty, but sometimes you have to do what it takes.
Less False Casting: Repeated false casts can be dangerous if not nearly impossible in blustery conditions. For this reason, "water hauling" or "water loading" provides a margin of control and safety. Instead of consecutively casting back and forth in the air to work the line out, you do it in increments.
Make a back cast as usual, but then make just one forward cast and let the line land in the water. As soon as it touches down, you repeat the process by going into another back cast, then make one forward stroke and lay the line back down on the water in front of you again. This two-step process is repeated, feeding out more and more line each time until the right amount of distance has been reached. It takes a little longer than traditional aerial false casting, but when it's windy it gives you much better line control and safety.
As you're working the line out through this process, it's very important that you pick the line up off the water very quickly each time—especially with a sinking line or weighted fly. On top of having to break the line free of the water's surface tension, wind/waves can blow the line out of whack and the fly and/or line can sink too much making it difficult to pull everything up out of the water efficiently, especially with the more line that you have out.
Backhand It: If the wind is blowing into your casting shoulder, using a backhand cast is often preferred because it puts the line on the downwind side of your body. To do this, you set yourself up so that you're basically facing away from your target and presenting the fly on the back stroke rather than the front stroke. I'm right-handed and normally cast with my left foot forward, so for the backhand presentation I'll instead put my right foot forward and turn my upper body the other way. Basically, it just looks like I'm casting normally but in the total opposite direction of where I want the fly to go.
I use this cast a ton while shore fishing in tight spots even when it's not windy because it gives me better aim to keep my casts between or over obstacles up on the bank than a typical back cast would. It's also highly-useful for fishing off a boat to keep the fly from smacking something like a console or your partner that would normally be on your typical casting side.
Shooting Line: You should not only be comfortable with feeding out line on the front stroke, but also on the back stroke, too. When the wind is coming at you head-on, feeding out line on the back stroke is often way easier since the wind is helping to blow the line in that direction anyway.
Leader Length: Wind can hamper fly turnover. To make things easier, try shortening the leader a little bit. Waves and silt kicked up from the wind can make fish less spooky anyway, so a shorter leader often doesn't pose any issues from a fish-catching standpoint.