Why do I feel pleasant after having a bottle of beer but after consuming whiskey I feel depressed?

I am not a habitual drinker. I like having beer once a week and only one bottle on saturday nights. Sometimes my friends offer me whiskey with water (1 large peg only) I start feeling depressed and giddy. I don't like going for 2nd peg. But after 1 bottle beer I feel lighter and in a pleasant mood. Why it is so !! I am so surprised although they both are alcohol based drinks. Is there any other cocktail which gives the same feeling like beer. Please suggest as sometimes the beer is not available, and I hate to take whiskey etc.