If you want to gain respect, especially as a young man, do whatever you can to keep your word. Respond to others promptly(within 24 hours at most), keep your commitments, do what you say you will. In our day of rampant flakiness simple things like following through will set you apart.

And if you fail, own up to it as quickly as you can. And then do better next time.

"But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation." James 5:12