Actually to be honest, all the majibu before me are part of love, but it is also part of attraction to the person. I mean one does get butterflies and feels nervous around a crush, but that does not mean wewe would feel the same way when wewe are in upendo with someone and they are in upendo with wewe back.
Truth be told, the feeling of being in upendo is different for everyone. The same common feelings like wanting to be with the person always and all that butterflies are still there, but when wewe are in love, it all intensifies, beyond what wewe imagined could ever happen before.
But above all else, being in upendo means putting someone before yourself and also telling yourself that I am worthy of such upendo from this person and I as a person would be able to give that upendo back. It's all about feeling that ability to give and receive as well as to care, sacrifice and respect.
wewe know you're in upendo when wewe think about that person all of the time, when you're moyo starts beating faster every-time wewe see him/her. wewe want them so badly it makes wewe want to scream. That's how wewe know.
You're in love- and I mean it- when wewe can imagine yourself spending your days at the side of your loved one. When wewe don't mind making sacrifices, when wewe know, wewe know, cause your moyo tells wewe and your mind agrees.