Money you can get back. Time, you cannot. Use your time wisely.
General society loves to teach people that they should be all starry wide-eyed and naive when in reality, this is a great evil; The actual anthesis of evolution.
When we are taught to be bubbly-wide-eye-go-lucky (and the flipside extreme of negative) then we have no real clarity, nor proper observation and we lack adequate judgement.
Don't waste your time with relationships that are clearly going nowhere. You should have a direct impulse from day one of where something can or cannot go. Pay attention to your innermost voice.
Humans aren't as clever as you'd like to erroneously believe. You don't need months or years to know if someone should be in your life or not. Train yourself to pay attention to the person(s) you're dealing with from day one. Observe their body language, pay attention to the tone of their voice (or if on computer: the frequency of their texts), etc.
Time is precious, why waste it on people who aren't on your wavelength? Better yet, why waste it with people who clearly don't align with your dreams and goals?