There is no doubt about it: Eating out - dining - outside your own home when you are on a diet can be very stressful. It is, admittedly, a challenge when you are a person that likes food. But, don't give up. There IS a solution to your problem.
Making Wise Decisions When You Read the Menu
You don't have to give up eating at restaurants, but you CAN make wise decisions when you read the menu. You don't become healthier by staying away from the challenge, but you WILL be a winner when you prove to yourself - and everyone else - that it IS possible to eat well without fatty sauces, deep fried potatoes etc.
Your diet is not only a question of losing fat, but is a change towards building NEW, and healthier, habits.
Days Without Meat
You can indeed focus on a good tuna salad or a ceasar's salad. Quite often, you will find that vegetarian dishes are absolutely excellent and having one day without meat won't kill anyone. Some, here in Scandinavia, have one weekly day where they various forms of porrage - and there are some pretty good varieties with almonds, oats or honey.
There is no need to feel guilty for choosing one of the dishes for people who are dieting. On the contrary, if you focus less on what you might have eaten you learn to enjoy your food while surrounded by temptations. It's like an ex-smoker who has thrown out all cigarettes. No cigarettes available doesn't mean you have given up smoking, but when you can have a pack in your car WITHOUT feeling any need to smoke it, you may call yourself an ex-smoker. You must make an active decision to avoid something for it to be a conscious choice.
Many delicious sauces are very difficult to resist for a lot of people. They are the type of fat many people never notice. Meat and chicken sauces might be somewhat better than a creamy Sauce Bernaise. Even if you do get a dish with some sauce involved, you don't have to eat all of it. We may live in cultures where people like to almost lick their dishes, but you don't have to do that. :-)
Look at your new focus on healthy foods as a form of quality control. Restaurants always have some form of salad, and when you begin enjoying yellow, green and red pepper, squash, aubergines etc everything becomes a lot lighter, and your body has a lot less work to do in metabolizing what you take in.
If you keep your manners under control when eating out, you will find that you win in more than one way by showing it CAN be done.