Your no earns respect when your yes is reliable.

Refusals carry weight in proportion to how much your agreement can be trusted. Promise widely and deliver unevenly, and a no sounds like one more unpredictable thing about you. Do what you said you would, and people hear a limit as information rather than as a mood. The two halves hold each other up.

Look at what you already agreed to this week and finish those things properly. Then decline the next ask without guilt, and let your record do the explaining for you.