Do your best not to let diction hold you back. If speaking clearly is a problem and people don't understand you, it's time to learn some tips. This is an issue which can be fixed. Your personal and professional life should not be affected by this. Too many people are hiding their talents and great ideas just because they are too embarrassed to speak up. The first step is to gain more self confidence.
To improve the clarity of your speech you need to slow down. Try to avoid speaking too fast. This will help the other person to understand you better. Make a short pause to clarify different sentences. A pause it's also required when you change the topic of your discussion.
You need to really speak up. If you are shy and cover your mouth with your hands or a book you will not succeed to speak clear. Stand up straight and talk with a louder voice. It's important to keep eye contact with the other person.
Always remember to articulate the word endings such as plural or past tense. This will make your speech more clear and without any grammatical errors. People are in a hurry and most of the time they fail to enunciate the word endings.
You can also do some easy reading exercising at home. Ask a friend to listen to you while you read loud from a book. You can also record your voice. You need to repeat every word slowly until you manage to speak clear. Try to consider this a sport. The more you practice the better you get.
One of the easiest trick is to use only short words. Try to avoid difficult long words when you can find an equivalent. This way it will be easy for you to speak clear and make your self understood. Follow this tricks and you will change your life. You will no longer be embarrassed for the way you're talking.