A daily training for your voice will strengthen your vocal cords, improve your vocal range and develop a better vocal tone. If you don't have a daily routine, work with your vocal coach to create one for you. With the correct placement of the voice and breathing, your voice will become stable and resonant. You can project it better, and soon, you will have the confidence to speak without any difficulty, even if you would talk for a long period of time.
The best thing you can do to improve your singing is to sing regularly. Singing every day strengthens your vocal cords, improves your vocal range and will gradually lead you to better vocal tone. Examples of musical tones could be C, D, E, F, G, A or B. Ingo Titze, a leading voice researcher, wrote an article called A Restricted use of a Mamallian larynx (Restricted use of a mammal's larynx) and explains that *not* using the voice to its full potential can lead to muscle atrophy.
Since the same physical mechanism and structures are used to produce your speaking and singing voice, any vocal habits you have acquired to improve your singing voice can also be used to improve your oral voice. Once embedded, these vocal techniques can transform not only your singing voice but also your speaking voice. So, you may be wondering, how can I make my voice sound resonant and rich without manipulating or straining my voice? Anecdotally, I can also say as a transgender woman that I really feel better (although this is probably psychological) talking in my female voice than with my male voice and I don't experience symptoms of fatigue beyond the initial tension of lifting the larynx, which disappeared after developing that muscle coordination and strength. You should look for your “real” or true voice that, in 99% of cases, has a deeper tone than the voice you have been using out of habit, your usual voice.
But, I'm not saying that I want my voice to sound exactly like her, no, I just want Ariana's tone level so I can sing in front of people and in love with my voice. Therefore, it is reasonable to maintain that improving your voice when singing would also improve your voice when speaking.