'sentir' is related with outer. You use it to explain that you perceive something that is out of you (like in I feel the wind)
'sentirse' (and other form verbs that fit in "something-something" + se) is related with inner. You use it to explain something about you (i.e your mood). Perceive something inside the limits of your body (like in I feel ill). Is not an exact rule (I feel pain uses sentir for example) but is useful.
'sentir' is related with outer. You use it to explain that you perceive something that is out of you (like in I feel the wind)
'sentirse' (and other form verbs that fit in "something-something" + se) is related with inner. You use it to explain something about you (i.e your mood). Perceive something inside the limits of your body (like in I feel ill). Is not an exact rule (I feel pain uses sentir for example) but is useful.