Fake it? Sure, you may not want to dampen the mood or drag your friends down. But faking a smile doesn’t benefit you (because you still feel annoyed) or your friends (who may see through your inauthenticity). Instead, try to genuinely change your mood so that you’re not pretending, and are authentically expressing more positive emotions. I mean, easier said than done, but you may consider therapy or simply doing some deep thinking about it. I mean, stuttering shouldn't and doesn't have to prevent you from enjoying life, simply put. Trust me, it might be tough, but you can get there.