If you can’t afford to lose it, don’t bet it on someone else’s promise.

Promises are only as good as the other person’s circumstances, and circumstances change without anybody intending harm. They lose the job, the car breaks, their parents say no, they simply forget. None of that was predictable from how sincere they sounded at the time. Risk what you could survive losing and keep the rest outside anybody else’s reliability.

Think about what you have riding on somebody keeping their word: money lent, a lift you are counting on, a group project where one piece is entirely theirs. Decide what you would do if each one failed.